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OSMANIA UNIVERSITY LIBRARY 

Call No. S~< ?> Accession No. 

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This book should be returrted on or before the date 
last marked below. 



HANDBOOK OF THE H HAVENS 




Dana K. Bailey, J.A.C. 

CIRCUMPOLAR TRAILS. A small camera, focused with a magnifier, was placed 
upon the ground and pointed at the North Star and its neighbors. In an hour's exposure, the 
stars revealed the rotation of the earth by recording on the photographic plate a fraction 
of the apparent daily circle of each. The group arrangement of the Little Dipper with the 
Pole Star at the end of the handle has been indicated at the initial position and the trails 
show its subsequent motion. This picture was made with a fine lens in the clear desert 
air of southern Arizona, and the original negative shows the trails of forty stars within the 
diurnal circle of Polaris. Anyone with even a box camera can make similar pictures. 



HANDBOOK 
OF THE HEAVENS 

SPONSORED BY 

The ? American *%Cuseum of D^atural History 

Editors 
HUBERT J. BERNHARD 

Director of Publication^ ftihior Astronomy Club 



DOROTHY A. 

Assistant Curator of thf llaydfn Planetarium', Adviser, Junior Astronomy Club 



HUGH S. RICE 

Associate in Astronomy, American. Museum, Sctrtl'fiJ'ic Associate , Junior Astrono 



WITH A * ORE WORD BY 

PROFESSOR HARLOW SHAPLEY 

l)irector t Harvard College Observatory 



New York WHITTLESEY HOUSE London 
MCGRAW-HILL BOOK COMPANY, INC. 



Copyright, 1935, by the McGRAW-HjLL BOOK COMPANY, INC. 

All rights reserved. This book, or parts thereof, may not be 
reproduced in any form without permission of the publishers 



SKCOM) PRINTING 



PUBLISHED BY WHITTLESEY HOUSE 
A division of the McGraw-Hill Book Company, Inc. 

Printed in the United States of America by The Maple Pres\ Co., York, Pa. 



To 
DR. CLYDE FISHER 

Curator of Astronomy 
American Museum of Naturaf^History 

in charge of 
THE HAYDEN PLANETARIUM 



CONTRIBUTORS 

DANA BAILEY ROBERT MILLER 

GIRARD BLOCK JAMES ROTHSCHILD 

RUTH FLEISCHER DICK SCHIRLING 

ROBERT FLEISCHER DOROTHY SCHOOF 

ANNESTA FRIEDMAN VERA WOLFSON 

Louis HEYNICK 

ACKNOWLEDGMENTS 

GRATEFUL acknowledgment is here made to the many people 
who have taken part in the preparation of this book. First 
thanks are due to the contributors, members of the Junior 
Astronomy Club at the American Museum of Natural History, 
whose genuine enthusiasm for their hobby of astronomy has 
made the book possible. 

We are indebted to Dr. Harlow Shapley for his unfailing 
interest and encouragement, and especially thank our many 
friends at the American Museum of Natural History. 

To Dr. Charles S. Adams, Director of Mount Wilson Ob- 
servatory, and to Dr. Otto Struve, Director of Yerkes Observa- 
tory, we are indebted for the photographic illustrations. 

The unique assistance rendered by Dean Guy Stanton 
Ford, Mrs. Chauncy Cooke, and Miss Anne E. Rumpf is 
gratefully acknowledged, as well as that of many others who 
have aided greatly in this undertaking. 

THE EDITORS. 

AMERICAN MUSEUM OF NATURAL HISTORY, 
September, i 



FOREWORD 

MY FIRST impulse in writing to the Junior Astronomers about 
their Handbook of the Heavens is to greet them in behalf of the 
profession and congratulate them on their unearthly interests. 
But the second is to warn them not to take the science too 
seriously. As an avocation, there is nothing more mind-cleans- 
ing than astronomy; as a profession, it is a hard master. 

The young student should first discover in himself a high 
talent for mathematics or for making experiments, or the 
possession of a constructive imagination, before he ventures to 
change his interest in stars and planets, lenses and mirrors, 
from a healthy hobby into a business. The amateur astron- 
omer and the unprofessional student are blessed with freedom 
from deadening responsibility; they answer only to the per- 
sonal urge to do or to know. They can observe and read and 
think of velocities, masses, distances, and durations that are 
uncommon to the inhabitants of the earth's crust. They can 
play, at least in thought, with meteors and galaxies which 
are so different in size, so similar in origin, meaning, and 
obedience to cosmic laws. In a life of petty turmoils, the 
Junior Astronomer, by detaching himself from the earth, is 
preparing for one of the highest enterprises in the realm of 
contemplation the wholly impersonal Dream. 

HARLOW SHAPLEY. 

HARVARD COLLEGE OBSERVATORY, 
CAMBRIDGE, MASS., 
September > 1935. 



XI 



CONTENTS 

FOREWORD, BY HARLOW SHAPLEY xi 

LIST OF ILLUSTRATIONS xv 

EXPLORING AMONG THE STARS 3 

STARS OF THE NORTH POLAR SKIES 5 

AUTUMN AND WINTER SKIES 12 

SPRING AND SUMMER SKIES 22 

STARS OF THE SOUTHERN SKIES 29 

EXPLORING AMONG THE PLANETS 37 

EXPLORING ON THE MOON 51 

METEORS AND METEOR SHOWERS 60 

COMETS 65 

DOUBLE STARS 69 

SOLAR OBSERVATIONS 74 

NEBULAE AND CLUSTERS 80 

VARIABLE STARS 88 

HINTS ON TELESCOPE USAGE 94 

ASTEROID HUNTING 101 

AMATEUR ASTRONOMICAL PHOTOGRAPHY 109 

OBSERVATIONAL SCRAPBOOK 115 

GLOSSARY 121 

INDEX 125 



xvi List of Illustrations 

Mare Imbrium Region of Moon 58 

Chart of the Moon 59 

Meteor Trail 61 

Meteor Radiant 61 

Halley's Comet 67 

Comet Debris 67 

Binary System 71 

Double Star Kriiger 60 73 

Sun's Disc 77 

Solar Eclipse , 77 

Great Nebula in Orion 81 

Ring Nebula in Lyra 81 

Great Nebula in Andromeda 82 

Horsehead Nebula in Orion 82 

Mosaic of the Milky Way. . . . . 83 

Star Cluster in Hercules. ... . . 84 

Double Cluster in Perseus 84 

Light curve of Delta Cephei 91 

Refracting Telescope, Equatorial Mount 95 

Chart of the Asteroid Vesta 107 

Chart of the Asteroid Juno . . . . 108 

Orion, an Amateur Photograph ....in 

Venus and the Moon in 

The Moon, an Amateur Photograph 113 

Ahnighito Meteorite 117 

Celestial Coordinates . 118 

In addition, there are 32 charts and diagrams which appear in the text 
but which are not listed here. 



HANDBOOK OF THE HEAVENS 



Exploring among the Stars 

IT is fun to watch the stars and to make friends with them 
to see the Big Dipper and to know that by this star picture 
Greek shepherds told the hour of the night, American Indians 
timed the planting of their crops, and Columbus guided his 
boat to a new world. 

Memories of the rough-hewn men who first looked to these 
stars for guidance and companionship return to us. And they 
conflict with thoughts of civilizations which will rise and fall 
under these same stars. That is the romance of the skies. 

Just as the bird lover rejoices to hear the notes of the first 
robin in the spring and the gardener smiles to see the early 
crocus pushing through the wintry soil, so those who have 
discovered companionship in the stars welcome the return of 
old favorites to the skies. Each hour of the night and each 
season of the year new stars come into view. 

Exploring on one's own, one finds among the star groups 
or constellations imaginary pictures outlined by the stars. 
Some are so ancient that they are found on Babylonian stones; 
others so modern they include an air pump. Perhaps the 
best known of the constellations are the zodiacal groups which 
form a backdrop of stars along the path which the sun, moon, 
and planets always seem to follow. In this historic region of 
the sky three new planets have been discovered by the watch- 
ful eyes of astronomers. There shines Venus, a blaze of glory 
in the morning or evening sky; and in the same path ringed 
Saturn creeps, spending two years in one constellation. The 
moon, too, wends its way among the animals of the zodiac. 

In one night of watching the stars we may become familiar 
with many of them. We may learn to know many of the 
constellations at sight. But then we have learned only the 
stars visible at that time. There are hundreds more. Later 
in the month or even later that same evening new stars will 

3 



4 Handbook of the Heavens 

have risen above the horizon. In one night we may see several 
planets. But there are others. In one night we may find fifty 
markings on the surface of the moon. But there are thousands. 

So all the nights of a lifetime are not enough to discover 
even half the secrets of the skies. We can learn only a few; 
always there remains something new, something unknown to 
lure us on. Perhaps some one of us may find something that 
has never been noticed before ! 

It may be this book will reveal to you the fascination of the 
stars. To that end it is written. 



Stars of the North Polar Skies 




DAILY swinging around the north celestial pole, never setting 
for observers in the latitudes of New York, are the keystones 
of constellation study, the circumpolar stars. Forming an easy 
guide to the location of other groups, they are in themselves 
of extreme interest. 

Most easily recognized and most important of all these 
constellations is the Big Dipper. Ursa Major, as it is known to 
astronomers, means Greater Bear, but no name could suit this 
group better than the "Dipper" for it looks exactly like one. 

5 



6 Handbook of the Heavens 

Four stars form the bowl and three the handle; and the 
resemblance is the more perfect since all but one of the stars 
are of the same magnitude. 

In this dipper the second star from the end of the handle 
is an object that carries us back to the days of the early 
Arabs. This is the star Mizar and its faint companion Alcor 
which form a naked-eye double. So difficult is it to see Alcor 
that this was the standard eyesight test given to recruits for 
the Arabian army. ** 

Although to the casual observer the bowl of the dipper 
may seem almost devoid of stars, a careful count with the 
naked eye on a clear night will reveal ten or twelve faint 
ones. In this area are located several famous telescopic 
objects. 

It is with the use of the Big Dipper, more widely known 
than any other group, that the Pole Star is found. By following 
a line drawn through the pointers of the bowl (the two stars 
directly opposite the handle), and continuing through the top 
of it one comes to Polaris, the North Star, guide of mariners 
for untold generations. 

Polaris, which is about twice the moon's apparent diameter 
from the true north celestial pole, does not stand alone in the 
sky; instead it is the brightest star of the Little Dipper, or 
Ursa Minor. This group is more difficult to make out than is 
its larger brother, for the stars are fainter and of varying 
degrees of brightness. Two, which occupy a position in the 
bowl similar to that of the pointers in the larger constellation, 
are fairly bright and are easily found on a clear night. They 
lie between the pole and Draco, and because they seem ever 
to be on guard against an attack by the dragon upon Polaris, 
they are known as the guardians of the pole. 

Draco itself starts in a rather faint star which is slightly 
nearer to the pointers than to Polaris and winds its serpentine 
length in a rough half circle around the Pole Star. Then, at a 
sharp angle to its former path, it rears its head, marked by a 
pair of prominent stars which might be taken for eyes, at 
Hercules. The Dragon provides a not-too-difficult group to 



Stars of the North Polar Skies 7 

hunt for and one which, as it gradually unwinds to the be- 
ginner, becomes more and more interesting. 

Polaris now is the North Star, but it was not always so. 
Owing to a "wobbling" of the earth's axis the north pole of 
the sky is constantly changing its position with respect to the 
constellations. Thousands of years ago Alpha Draconis, one 
of the dimmer stars in Draco, was the Pole Star, and at some 
date far in the future the bright star Vega, which now shines 
in the summer skies, Will be near the pole. 

Across the pole from Ursa Major, and equally distant from 
Polaris, lies a group of stars that resembles a big chair. This is 
Cassiopeia, better known as the Seated Lady. Its startling 
resemblance to a W is enhanced by the fact that nearly all 
the component stars are approximately of the same brilliance. 

Cassiopeia, like all the constellations, is more than an 
outline of bright stars visible to the naked eye. It encompasses 
a sky area in which are numerous stars of various degrees of 
brilliance. All the stars are classified according to their bright- 
ness and grouped in magnitudes. A star of the first magnitude 
is 2^2 times brighter than one of the second magnitude, and 
this proportion is used throughout the scale. Stars brighter 
than first magnitude a?e reckoned below zero, given propor- 
tional negative values, and designated by a minus sign. Thus 
the highest number represents the least brilliance and Sirius, 
our brightest star, is 1.58. At the other extreme are the faint 
sixth-magnitude stars beyond which the unaided eye cannot 
see. 

Telescopes have revealed objects down to the twenty-first 
magnitude and they have also revealed in many cases two or 
more stars where only one was visible to the unaided eye. 
Such a double star is Eta (77) Cassiopeiae, so called after the 
common practice of using Greek ' letters to designate the 
different stars in the constellations. Even stars so well known 
as to have proper names of their own are also given Greek- 
letter designations; thus Sirius is Alpha (a) Canis Majoris. 

Perseus is interesting because it is the radiant point for 
the August meteor shower that bombards the earth with 



8 Handbook of the Heavens 

countless shooting stars each year. It is only partly circumpolar 
for these latitudes, for here a greater part of it dips below the 
horizon for a short time every day. To be entirely circumpolar 
an object must have a polar distance that is less than the 
observer's latitude. Wherever one is on the earth's surface, 
his celestial pole is as far above the horizon as his latitude. 
Thus a person in the latitude of New York, 41, would 
count circumpolar all stars within 41 of the north celestial 
pole. 

Perseus contains two stars which vary in brightness within 
the limits of naked-eye observation. One is Rho (p) Persei, 
which ranges through a whole magnitude in about a month, and 
the other is Beta (/?), the famous Algol, or Demon Star, which 
changes as much in a few days. 

Between Perseus and Cassiopeia lies one of the most 
interesting objects for amateur observation found within the 
circump6lar boundaries. This is the double star cluster Chi-h 
(x-h) Persei. Faintly visible to the naked eye under good 
conditions, it becomes an object of beauty when seen through 
an opera glass. 

Two other less prominent constellations fall into the cir- 
cumpolar group, Cepheus and Camelopardalis. Cepheus may 
be located by continuing the line from the pointers of Ursa 
Major through the Pole Star and extending it on for about 
once again its own length. This will take the beginner to a 
previously unexplored sky region, and in it he will find a rude 
lantern composed of third- and fourth-magnitude stars. 
The Milky Way runs through Cepheus, and in the constella- 
tion are found several interesting double stars. Among these 
is Delta (5), which is not only a yellow-and-blue double but 
also a famous variable star after which the Cepheid type 
of variable was named. 

Lacerta, Lynx, and Camelopardalis are real challenges 
to the sky explorer, for they are all composed of exceedingly 
faint stars which are not arranged in any striking formations. 
In an effort to build Camelopardalis up from nothing, locate 
Alpha and Beta, and from these, with the aid of the connecting 



Stars of the North Polar Skies 9 

lines on the charts, the rest of the stars can be found. But even 
this elusive group can be observed on any very clear moonless 
night during the year and so it should soon become as well 
known as its more prominent neighbors. 



Stars of the Autumn and Winter Skies 




The map above shows positions and accepted geometric patterns for all the constel- 
lations visible at 9 P.M. November I in latitude 40 north. Identification of the star groups 
may be made by comparison with the chart on the opposite page. 

In use, this map should be held overhead and oriented according to the compass points 
indicated. It will then show the stars as they appear in the sky. The stars visible here at 
9 P.M. November I will also be visible at 7 P.M. December I and at n P.M. October i as 
explained in the chapter on "Autumn and Winter Skies." 

10 



Chart of Autumn and Winter Skies 



N 



Urse* Major 



< V-4-* ^N 

jorV'''' >..- 



Lynx 



1 J i u*mej<*par/*fohs . 

I Gefnini r"\a /Q \*'Y \"7^ L 

^ / ^ ^ ! v: V u3 

* /I ^.^W *'-~*''^. ** '' m IA 

Aur \6ifc* t"f" ml--* tf^ 




{ r ,/ J ,/ . Nr 

\ ,/ PbCTrf. 6" Drflc ^!7 ,.- v "^>- 

. ot'''../.. -^ ^ Hercules.- 



a / 



f 



*T 



* 

v- 



Taurus 



% ^. 

Delphinus 



v Tec ' ueipnn 

Aries; r-*55 .' Pegasus ^ 

<^-\ / -^^ / <> 



Erid^nu^ \Cctus 

-,> x:\ 

.V r --v 



Forn^ix 



Sculptor Piscis V> 

^ * N Aus+rin r ' 




w 



The map above shows the accepted geometrical patterns of all the constellations visible 
at 9 P.M. November I in latitude 40 north. All the stars listed for study in the chapters on 
"Double Stars" and "Variable Stars" are indicated, as are the first-magnitude stars, which 
are the following: 

a Geminorum Castor a Tauri Aldebaran a Aquilae Altair 

ft Geminorum Pollux a Lyrae Vega a Piscis Austrini Fomalhaut 

a Orionis Betelgeuse a Cygni Deneb a Aurigae Capella 

ii 



Autumn and Winter Skies 

DURING the cold winter months the display of brilliant stars 
dotting the night skies is at its best. But really to learn 
the winter constellations one must start in autumn and 
continue on into the season of snow and ice, thereby gaining 
an understanding of the transitions that take place in the 
heavens. 

Early in the evening, just around the time that autumn is 
officially ushered in, we find the impressive Northern Cross, 
embodied in the constellation of Cygnus, directly overhead. 
With its first-magnitude star Deneb, the Cross is easily traced 
among the stars, and at its base is found the beautiful double 
star Albkeo. 

Near Cygnus is the small constellation Lyra, which con- 
tains within its borders the blue-white star Vega. Both Vega 
and Deneb will be setting in the west later in the evening at 
this time of the year, for they belong with the summer stars. 
The brightest of the summer stars, Vega, as it sets will be 
superseded by the even more brilliant Sirius, rising in the east. 

Aquila, the Flying Eagle, is southwest of Cygnus and in 
it there is the first-magnitude star Altair. This is a white 
star, and it may be distinguished in that it makes a triangle 
with Vega and Deneb. 

Northeast of Aquila is a small and not so important con- 
stellation, Delphinus, the Dolphin, or Job's Coffin. In this 
is a cluster which is estimated to be 220,000 light years away 
one of the most distant objects known until recently. The 
limit of visibility now extends 2,000 times this distance and 
objects may be photographed which are 500 million light years 
away. 

Somewhere about halfway between Cygnus and the eastern 
horizon a great square of bright stars fills the sky. This is 
Pegasus, the Winged Horse, and the area within the boundaries 

12 



dutumn and Winter Skies 



DELPHINUS 






V CYGNUS 



x > V \ Ring Nebula.^ LYRA 
,/AQUllA* 



-M3. 



ARIES/ 

/ PISCES 
/ >--~"~-., 



PEGASUS 
^ j 






of the square presents a challenge to the observer. Under 
ordinary conditions only a small number of stars can be seen, 
but under ideal conditions as many as eighty have been 
identified with the naked eye. 

Extending from the northeast corner of Pegasus is part of 
Andromeda, which contains the only spiral nebula in the whole 
sky visible to the naked eye. The nebula is marked M 31 
in the accompanying diagram. Between Andromeda and the 
horizon is a little triangular group of fainter stars appropriately 
named Triangulum. Directly south of Triangulum lies Aries, 
the first zodiacal constellation. 

Looking along the zodiac to the west of Aries, we find the 
stars of Pisces. The rather faint stars are difficult to identify 
but the constellation is an important sky mark, for in it is 
located the vernal equinox, a reference point for the positions 
of all celestial objects. 

Somewhat toward the south and coming up on the eastern 
horizon is Cetus, the Whale. In this larger group is found the 
famous variable star Mira which is at times as bright as Polaris, 
then fades to the limit of naked-eye visibility, and finally drops 
from view except in a telescope. Stars of this type, which vary 
in brightness, are discussed more fully on page 88. 

The Pleiades, in Taurus, the Bull, consist of seven stars, 
almost universally known. To the Babylonians they were 
"the many little ones"; to the Greeks, "the seven sisters"; 
to the American Indian "the seven brothers"; and so on. 
Actually, there are about 250 stars in the cluster, but even on a 
very clear night only seven can be distinguished without optical 



Handbook of the Heavens 




CETUS 



ERIDANUS' 

,-*-*v / 

f ** 



aid. Sometimes it is hard even to see the seventh star, which 
is called the "lost" sister. 

The month of November is known as the Pleiad month 
because the Pleiades are prominent in the eastern sky early 
during the evening. Later the same evening the stars will 
climb toward the south, reach their highest point, and sink 
in the west, retracing the path laid by the sun twelve, hours 
before. The westward motions of sun and stars are apparent; 
the true motion is that of the earth as it turns eastward on its 
axis every twenty-four hours. Thus new objects are coming 
into view on the eastern horizon all night long. 

The rising and setting of the stars are also affected by the 
earth's yearly revolution around the sun. As a result, in every 
two hours of watching on any night observers may see objects 
visible one month later during the two preceding hours. For 
example, a person observing between the hours of 10 and 
midnight on July 4 will see the stars visible from 8 to 10 on 
August 4. Similarly, on any morning from 3 to 6 A.M. one can 
see the evening stars of the coming season. 

Another group of stars found in Taurus is the Hyades 
almost as well known as the Pleiades. This is a V-shaped cluster 
with the first-magnitude star Aldebaran at the lower end. 
Aldebaran is a fiery-red star visible for eight months of the 
year. It is frequently obscured from our view by the passage 
of the moon between it and the earth. This occultation, as 
such a happening is called, is striking to watch. 

Fomalhaut moves across the southern evening sky during 
the autumn months, but when winter begins it is no longer 



Autumn and Winter Skies 



Be+clgeuze mf* 



<J 






^ jf ^' 

CANIS MINOR /->- \ <fc < 

^v \ . / ; 1424 
a-- s H/ / ' v 

4/ > i Bi ..-.::;.-^ .<_ / 

Procyon / / "" f "/^ 

A y ^MO^OCEROS ij 

{ " /; y v r "T Sinus 

: /*t637 CANIS MAJOR^ 

t -f.V" * 

> /-? 4>< 



>. 



visible. It is the brightest star in Piscis Austrinus, a constella- 
tion composed of faint stars. This group can hardly be traced 
in outline from these latitudes, although Fomalhaut is of the 
first magnitude and is a conspicuous sky mark. 

One of the most striking of the constellations, Orion, lies 
just below the horizon, soon to reveal itself. Toward the end 
of October it can be seen rising at 9 o'clock. As it comes into 
view, the groups of Hercules and Ophiuchus are sinking in 
the west, and Fomalhaut has traveled two-thirds of the way 
across the southern sky. 

Betelgeuse forms the right shoulder of Orion and is one 
of the few stars mentioned by name in the Bible. Bellatrix, 
neither so well known nor so bright, forms the left shoulder, 
while Rigel, blue-white and a star of the first magnitude, 
lies at the left foot of the hunter or warrior depicted by the 
group. 

Orion can easily be found in the sky by looking for three 
stars, all of the second magnitude and in a straight line, which 
make up the belt. In the sword attached to this belt is a 
beautiful nebula, one of the two in the northern skies that can 
be seen without optical aid. Of the three objects in the sword, 
it is the central one, Theta (0) Orionis. 

Almost squarely beneath Orion's feet is little Lepus, the 
Hare; and Eridanus, the River, also has its source in this 
region. Beginning at the blue-white star Rigel, it passes below 
Taurus and winds beneath Cetus, the Whale. No very con- 
spicuous stars mark these two constellations but they are 
interesting to find, as is near-by Columba. 



i6 



Handbook of the Heavens 



Castor 



GEMINI 
M35 



CACER \ 



<r 



t 

\ 

PYXIS 





COLUMBA 



When Gemini, located to the northeast of 'Orion, rises 
entirely, it appears as a long, rectangular group of stars. The 
constellation is commonly known as the Twins because 
of its two important stars, Castor and Pollux. Pollux, a slightly 
yellowish star, is the brighter of the pair but this was not 
always so, for at one time Castor was the brighter. 

The Twins, of second and first magnitude, respectively, 
are only about 4^ apart and therefore easy to locate in the 
sky as a pair. An interesting thing about Castor is that it is a 
magnificent double star, whose white components are of 
nearly equal magnitude. These two stars can be separated 
easily with the use of a small telescope. 

The Twins lie in the zodiac between the star groups of 
Taurus and Cancer. This zodiacal constellation is a very 
interesting region of the sky, for near Eta Geminorum, Uranus 
was discovered by Herschel in 1781, and near Delta Gemi- 
norum, Pluto was identified by the Lowell Observatory staff 
in 1930. The moon and the planets traverse this region con- 
stantly and are often found within the rectangle. 

South of Gemini lies the first-magnitude star Procyon, 
the brightest star of the diminutive constellation Canis Minor, 
or the Little Dog. Between it and the horizon is its, big brother 
Canis Major, the Big Dog, containing the brightest star in 
the heavens, the brilliant blue-white Sirius. 

Between Canis Major and Canis Minor is Monoceros, the 
Unicorn, composed of faint stars. This can be located with 
the aid of the star maps as can Puppis which is almost touching 
the bottom of the Dog Star group. It formerly was the poop of 



Autumn and Winter Skies 



f S 

r-v ^ X 




f ^ \ f .^ /""*" 

1 / 1 Achcrnr 
I N V r/> 


M37^ H 38 '' 1 ' 
^-_ AuKlGA ^ 




r o^ T ' ER'lDANUS 

V 

\ 

o^Rigel in ORION 



the great ship Argo Navis, which has been split up into several 
sections, of which Puppis is the most prominent to be seen 
from our latitude. 

Cancer, the Crab, is the next zodiacal constellation to 
come up over the horizon after Gemini, and in it is the famous 
Bee Hive cluster, Praesepe, which is visible to the naked eye. 
A diagram of Cancer with the location of Praesepe appears 
on page 16. A zodiacal group, Cancer acts as host to many 
of the planets and the moon. 

Almost overhead at 9 o'clock on early February evenings 
is Auriga, the Charioteer. With its extremely bright yellow 
Capella it is easy to locate. This group, rich in clusters, is 
right in the middle of the Milky Way. It narrowly missed 
being circumpolar and has some stars within the boundaries 
of the circumpolar groups. 



Stars of the Spring Skies 




The map above shows positions and accepted geometric patterns for all the constel- 
lations visible at 9 P.M. March I in latitude 40 north. Identification of the star groups may 
be made by comparison with the chart on the opposite page. 

In use, this map should be held overhead and oriented according to the compass points 
indicated. It will then show the stars as they appear in the sky. The stars visible here at 
9 P.M. March I will also be visible at 7 P.M. April I and at 11 P.M. February i. 

18 



Chart of the Spring Skies 




r* N 

"^ 



Lacerta 



?<^~ 



/'-A \ A^V"" 

f \E/ y ^ 

i -.., " rvCephcus 

1 1-4^. //* . 



D C t Ursa Minor ^ ^ a 

D^UK.'C TV 



^ 

b 



UrsoT^. Major 




Ancfrome0 

Polaris ^ j '' X 

Cassiopeia 7*'Trian0ulum 



< V^l^il9 VtllMIILI . ~ 




.^ 


E 

Coma* * Berenices 




A* 

L/nx 




"** 

; Leo Mi nor 
\ u:L * :: / jr-1 


/ 


: 


^^ 



1 N^:-- v 

V.* f j 



Aries 



W 



_ 



Vi T . ".r L \* '-^/r "^"'nini 

;- -f-*.,/ - T *\ ^nccr f X 

\ * Canis X A% * . ^ tridyius 

\ ^ **-fr Minor^''^""'" \*I\ ^ r '' 

\ ^ Corvus *-*! <.' jf \ js>p / 

\"^ *L_ Qovf/nrie T ** _,^t=--___ _ *.4Si . / 




Pyxis '^ ; /Puppis 




, 

...XV Szr -V V'Orion 
Mondceros 
* 



The map above shows the accepted geometrical patterns of all the constellations visible 
at 9 P.M. March i in latitude 40 north. All the stars listed for study in the chapters on 
"Double Stars" and "Variable Stars" are indicated, as are the first-magnitude stars, which 
are the following: 

a Aurigae Capella a Geminorum Castor 

a Leonis Regulus /3 Geminorum Pollux 

a Tauri Aldebaran a Orionis Betelgeuse 

19 



/3 Orionis Rigel 

a Canis Majoris Sirius 

a Canis Minoris Procvon 



Stars of the Summer Skies 




The map above shows positions and accepted geometric patterns for all the constel- 
lations visible at 9 P.M. July I in latitude 40 north. Identification of the star groups may be 
made by comparison with the chart on the opposite page. 

In use, this map should be held overhead and oriented according to the compass points 
indicated. It will then show the stars as they appear in the sky. The stars visible here at 
9 P.M. July I will also be visible at 7 P.M. August i and at 1 1 P.M. June i. 

20 



Chart of the Summer Skies 



s ^Andromeda 
'/ ?A* 

** 



V,*"** N 

terseusX ~* \ a" H -^*N 
n/ 1 f ^ Auriga 

* * * 



>, 



.^ Cassiopeia '* Camelopardalis % ^ v 

Pegasus <J * * Polaris > 

/ -4 * &' V ' * Ly \ 

//" fl \ *~'^ Vpheus ; Ursa Minor 
/ \*Lacerta _ V - ?-f, 



Cygnus f 



fft *'* f' I ? Ur$a Major 

Draro /'' .^ i"*^ / 



y rf 



i; 



Eciuuleus " s.VSagitta I u l> * iw v '^ Coma ^Berenices W 

* a t- * *%'' '' ^3 N ? s>% * T * 

/Aquarius ^ i ~* Herculesj \ Corona V-^ \ 

"' ^ >A ., L * ^iSL^e ^ / 

lAquila ^ *tt <4 ^Dootes -^ ^ 

x ^(JJ L /) 4 ""^ *L /I 

K Capricornus S ', \ r r\/"C"*T"* / 

V ^X \ Ophiuchus\ : Virgo / 

\ v.^ \ \ > 4 *<y w " ^.-'"* a r r 

\ Scutum *> /, S /X Corvus I .' 



nfttarius 



/ Scorpio 




The map above shows the accepted geometrical patterns of all the constellations visible 
at 9 P.M. July i in latitude 40 north. All the stars listed for study in the chapters on 
"Double Stars" and "Variable Stars" are indicated, as are the first-magnitude stars, which 
are the following: 

a Aurigae Capella a Aquilae Altair a. Bootis Arcturus 

a Cygni Deneb a Leonis Regulus a Virginis Spica 

a Lyrae Vega Scorpii An tares 



Spring and Summer Skies 

AN ever-changing vista of constellations moves across the 
darkened night skies as the earth pursues its yearly course 
around the sun. From Orion, setting in the western sky in 
the early evening on May i, around again to Orion rising 
in the east on November i, an amazing display of objects 
outlined in the stars is revealed to the eye. 

Let us look at the heavens on an evening early in spring 
at about 9 o'clock. In the west Orion is about to set, and Sirius 
will also be sinking in the southwest, while Perseus and 
Cassiopeia are in the northwest. Auriga, Taurus, Gemini, 
Canis Major, and Canis Minor, all among the autumn-winter 
stars, still stud the western half of the heavens. 

Turning from these groups toward the south, and looking 
up at a point nearly overhead, we see Leo, the brilliant Lion. 
Worshiped by the ancient Egyptians because the sun entered 
it about the time of the inundations of the Nile, Leo is one 
of the oldest of constellations. Regulus, the Little King, 
brightest star in the group, has a history of its own since it 
w#s by measurements of the longitude of this star that, 
thousands of years ago, the precession of the equinoxes was 
discovered. Eleven times as bright as the sun, Regulus is a 
double star but its eighth-magnitude component is unfortu- 
nately not easy to observe with a small telescope. 

Gamma (7) Leonis, second brightest star in the Sickle of 
Leo, is one of the finest double stars in the sky. Although it 
cannot be seen with a field glass, it can be resolved in a 3-inch 
telescope on clear nights. The colors are yellow and green. 

The Leonid meteor shower appears to emanate from this 
constellation, radiating from a point within the sickle. The 
planet Neptune, moving through the zodiac, has been in Leo 
for a number of years and it is gradually working its way 
eastward. 

22 



Spring and Summer Skies 



LEO MINOR 



Dtneboi" LEO > "7.. ,'fl\ L iBRA 

4(X o ' _'' P N xL- 1 OKA 

Regulus 
T 



t 

t -..VIRGO \ 



Following Leo across the heavens is Spica, the brightest 
star in the constellation of Virgo. A large and perfectly shaped 
Diamond of Virgo is formed in the sky by the stars Spica, 
Denebola, Cor Caroli, and Arcturus. Big though it is, Virgo 
contains few brilliant stars, and its chief interest is to the 
telescopist who can find in it many nebulae. Since the group 
is one of the zodiacal constellations, it contains within its 
borders at various times all the planets, the moon, and the sun. 

Marked by the blazing Arcturus, Bootes is located a short 
distance northeast of Virgo. It is surrounded by the stars of 
Corona to the east and Canes Venatici and Coma Berenices 
to the west. Although its shape suggests a giant kite, Bootes is 
supposed, in mythology, to represent a farmer behind his plow. 
Arcturus is the giant yellow sun whose light was used to open 
the 1933 World's Fair at Chicago. 

The constellation Canes Venatici, a misty patch of stars 
located beneath the handle of the Big Dipper, is known as 
the Hunting Dogs in mythology. Cor Caroli, third-magnitude 
and the brightest star in the group, is an interesting object in a 
small glass. It is a double with a sixth-magnitude companion. 

A little group of faint stars romantically named "Berenice's 
Hair" (Coma Berenices) can be found between Leo and 
Arcturus. Only five or six of the group are visible to the naked 
eye and they fail to form any easily recognizable pattern. 
The number of stars in the constellation takes a startling jump, 
however, when the region is viewed with a field glass which 
will show from twenty to thirty stars, including several 
doubles. 



Handbook of ihe Heavens 



J 
/ 




o AJcor a 


^ f $ r 






\^U* ' B J 6TES \ 
U.VA CORONA% XX X H \ 




*' ' Z * r URSA MAJOR 
Cor enroll 


?<* / \ *** %XN ' N 




OL+~"* 


T w '' (v 




CANES VENATICI 


HERCULES V^ ^ j' 






a l 




COMA, V ^ : BERENICES 


/ 




4 



Stretching over a long distance south of Cancer, Leo, and 
Virgo, lies Hydra with a pentagon of five faint stars marking 
its head. Although it twists its way southeast among the 
constellations for a distance equal to one-third the way 
around the sky, Hydra presents only one bright star to the 
observer. This is Alphard, a reddish star of second magnitude, 
which is known both as the Solitary One and as Cor Hydrae, 
the Heart of the Serpent. 

Rivaling in dimness the stars of the Serpent, upon whose 
back it rests, is the four-star group of Sextans which is so small 
as to be overlooked. It represents for it is of modern origin 
a scientific instrument, the sextant. Farther back from the 
head of Hydra, nearly southeast of Regulus, lies Crater, 
another small and inconspicuous constellation. Because of 
the fact that its most brilliant star is only of the fourth magni- 
tude, this little group is best observed on a dark, moonless 
night. 

A group closely associated with Crater is Corvus, the Crow, 
which is near the tail of Hydra. Its stars are somewhat brighter 
than are those of the groups with which it is identified, and 
it is arranged in an eye-catching quadrilateral. Delta Corvi 
is a pretty yellow-and-purple double. 

Corona, the Northern Crown, is a small circlet of stars 
located close beside Bootes. Despite the fact that with the 
sole exception of Alpha it is composed of fourth-magnitude 
stars, this little group presents an unusual and striking appear- 
ance, similar in a way to a horseshoe, and most people find that 
having seen it once they look for it continually. 



Spring and Summer Skies 25 



N ^'' SEXTANS 

CORVUS 

% 4 ""^ 

N..^ % ,5^ *> ^ : CRATER 

HYDRA^ V X *..4 ^-f > ^ k a.^ 

\ \ / "- ^ 

o 

...-" 



If you should be observing in the middle of July, a great 
change would greet your eyes. Looking west, you could recog- 
nize Spica, Arcturus, Corona, and the Big Dipper, but in the 
east would be a set of entirely strange constellations. 

Vega, most striking of all the newly risen stars, would 
almost certainly be the first to catch your eye. Surpassed in 
brightness only by Sirius which rises later in the year, this 
beautiful blue-white star will be about two-thirds of the 
way toward the zenith, or overhead point. It marks the 
approximate point on the celestial sphere toward which the sun, 
together with the solar system, is speeding at a rate of 12^ 
miles a second. 

A small and faint parallelogram of stars combines with 
Vega to form the constellation of Lyra. Although they are few, 
these stars are packed with interest. Epsilon (c), a naked-eye 
double to very good eyes, is a quadruple in the telescope; 
Beta's fluctuations in brightness are visible to the unaided 
eye; and Delta and Zeta (f) are also doubles. Zeta is magnifi- 
cent in low-powered instruments and Beta, in addition to its 
variability, becomes a quadruple star when seen with a 
telescope. 

Set in the luminous Milky Way, Aquila, the Eagle, is 
at this time about halfway between the horizon and Vega. 
Altair, its brightest star, forms a triangle with Vega and 
Deneb, of Cygnus, which also lies in the Milky Way. Cygnus, 
the Swan, is more widely known as the Northern Cross, with 
Deneb marking the top of the cross and the famous double 
Albireo the bottom. Glorious star fields pervade this region. 



Handbook of the Heavens 



^ SERPENS) 

; % "\ 
SERPENS I 
Q^JCcxuda \ 

* \ OPHIUCHUS j 
\ \ v / 

r; \ \ X 

v N ^ >' 

SCUTUM V V 



r/ CEPHEUS l-t f 

'CASSIOPEIA 1 '^- , DRACO 



LACERTA / , CY6NUS' 



Between Corona and Lyra is the constellation of Hercules. 
It necessitates gymnastics, but if, when the group is due south, 
you turn toward the south and then bend your head 'way back, 
you will see Hercules as the ancients saw him, kneeling with 
one hand upraised. The group contains the wonderful cluster 
M 13. 

Covering a large portion of the space between Hercules and 
the southern horizon is an immense pentagon of fairly promi- 
nent stars which form the constellation Ophiuchus. The group 
represents a physician who is holding a serpent, the constella- 
tion of Serpens, in his hands. 

Ophiuchus just borders on the Milky Way, which may be 
seen on a clear, moonless night. Starting at its northern end, 
we find Cassiopeia, and somewhat farther to the south is 
Cygnus. 

Between these two groups is a small house-shaped affair 
with the top of the house pointing to the pole. This is Cepheus, 
which contains Mu (ju), the fifth-magnitude Garnet Star, 
famous for its deep-red color. It makes a startling contrast 
with the white Alpha Cephei. Delta Cephei is a most interest- 
ing type of variable, the first of its kind to be studied. Also 
in this group is one of the "coalsack" or dark nebulae which 
are found along the Milky Way. Beyond Cygnus the Milky 
Way divides into two branches, one going through Sagittarius 
and the other through parts of Scorpio. 

As this striking constellation Scorpio climbs to its greatest 
height above the southern horizon, its- bright-red star passes 
the meridian. That bright-red star is Antares, the largest 



Spring and Summer Skies 



V 



v --,, 

\ 



Piscis CAPR1C RNUS 

AUSTRINUS 



SAGITTARIUS 



r*>" \ o> Anto.res ! 

*"' K-^" A 



C S SCORPIO 



star known, and although it stays close to the horizon now it 
will, because of the precession of the equinoxes, in a few 
thousand years climb high into the heavens for these latitudes. 

To the east of Scorpio is another important summer group, 
Sagittarius, the Archer. It boasts no first-magnitude stars, 
but it lies in the Milky Way with the Scorpion, and both groups 
therefore contain much telescopic material. They are also 
distinguished by the fact that both are zodiacal constellations. 

Lying along the path of the ecliptic between Scorpio and 
Virgo is the group of stars called Libra, the Scales. They are 
supposed to represent the Scales of Justice, and the name also 
bears some relation to the fact that when the sun is in this 
portion of the sky the days and nights are of equal length. 
Of the four bright stars here, two are interesting. Beta has a 
greenish color unique among naked-eye stars and Alpha is a 
field-glass double. 

On the opposite side of Scorpio and Sagittarius, and also 
in the zodiac, are Capricornus, the Sea Goat, and Aquarius, 
the Water Bearer. Both are easily found with the aid of the 
star maps published here. The faint stars of Capricornus 
cannot be seen except in a clear sky because they are too dim 
to penetrate haze and are easily blotted out by the glare of 
street lights. An occasional passing planet serves to mark the 
location of this butterfly-shaped group. 

Near the end of August, Fomalhaut, first-magnitude star 
in Piscis Austrinus, and the southernmost first-magnitude 
star visible from New York, rises above the horizon. It never 
climbs high, nor does it remain visible for more than a few 



28 Handbook of the Heavens 

hours at best, so it must be looked for at the proper time lest 
it be missed. 

In July, late in the evening, Pegasus and Andromeda, two 
constellations considered as sure harbingers of falling leaves 
and autumn winds, are beginning to rise. And when, right 
below Andromeda, Triangulum and Aries come into view, 
we know that autumn is actually at hand, bringing with it 
new star groups. 



Stars of the Southern Skies 

SOUTH of the equator, where the constellation of Orion depicts 
a man standing on his head, there are dozens of star groups 
that cannot be seen by observers in northern latitudes. 

But in the most southerly parts of the United States, the 
Southern Cross (Crux) rises above the horizon for a short 
time, and Canopus, the second brightest star in the heavens, 
is visible, shining with a peculiar intensity. 

The Southern Cross is preeminent. To persons below the 
equator it takes the place of Ursa Major and provides a 
celestial timepiece, reaching its highest southern point on 
the meridian at 9 P.M. on May 15, when it is almost perfectly 
erect, leaning very slightly to the east. 

Crux is clearly outlined by four stars of almost equal 
brilliance, and its likeness to a cross, therefore, is much more 
distinct than is that of its northern counterpart. Gamma is 
at the top of the cross, Alpha at the foot; Beta and Delta form 
the arms. No star marks the intersection of the arms although 
within the boundaries of the constellation there are about 
thirty-two stars visible to the naked eye. 

Its beautiful ruddy hue makes Gamma striking to the 
eye but negligible on an ordinary photographic plate. Because 
of its color it does not photograph well except on red-sensitive 
plates, and this is the reason for the usual disappointment 
people experience when examining pictures of the Southern 
Cross. Kappa (K) Crucis, also deep red, is in the midst of a 
fine cluster of about 130 stars, which are tinted in practically 
all the colors of the rainbow. 

A very interesting feature of the Cross is a coalsack nebula 
which is situated just due east of Alpha and covers a sizable 
constellation area. It is known as the Black Magellanic Cloud 
and is in that part of the Milky Way which runs through 

the Cross. 

29 



Stars of the Southern Skies 




The map above shows the positions and accepted patterns for the constellations within 
50 of the south celestial pole. Identification of the star groups may be made by comparison 
with the chart on the opposite page. 



Chart of the Southern Skies 




T3 

O 
63 

D 



lN \ 4 '' X / / > tf 

2 >V ; South A* 

;> .r < Celestial Pole< / ^. 

j- \ t(^i / 

TS ^ \ Mcns^f . 

n ~ s& *--"" " A . / *^.. 



* t- r 

^ 

% * 



:i < \ . v >' 

V^ ^^'4. ,/ ,# 
->- \ ..-''-' I// ' 

N> , \^ * J 

^ \ \^ D,VJ-^ : ~< 



1 C ^m 



1 ~ -e 

Pictor | ^- 



The map above shows the accepted geometrical patterns for the constellations within 
50 of the south celestial pole. All the stars listed for study in that chapter are indicated, as 
well as the first-magnitude stars, which are: 
a Carinae Canopus /3 Centauri 

CL Eridani Achernar a Crucis 

a Centauri Crucis 



32 



Handbook of the Heavens 



f V 



VOLANS 



,A* 

f* \ 

VELA\ 



,5 
47 S L HYDRU5 .*, .f Dor M 

JOUCAN .^.V/.^"""*""* ; ' : '-V :? ;. vi 
*"*^ .;'.; /'LESSER ' '''' ' ' ' /l\ 



Achern^r 



.. , 

f "V Magellan ic,' ; 
! V^ud I ; 

x ^\ 4 / 

RETICULUM* '/ 

DORAQUS 

i 



Drawing a line from Delta and extending it through Beta 
Crucis, one encounters Beta and Alpha Centauri. Centaurus, 
the Centaur, is one of the largest constellations in the southern 
sky, measuring in length about 45 or half the distance from 
the horizon to the overhead point, the zenith. 

The two brightest stars in Crux are the second and fourth 
brightest stars in the southern sky. Alpha Centauri, one of 
the mdst widely known stars in the whole heavens, is the 
third brightest of the naked-eye stars. Before the year 3000 B.C. 
Egyptian temples were oriented to it. It is a double star, our 
second nearest neighbor in the stellar universe. Its faint 
companion, Proxima Centauri, is the nearest star to the sun, 
having a distance of 4.16 light years. This indicates that it 
takes light, traveling at 186,000 miles per second, 4.16 years 
to bridge the distance between the star and the earth. 

The most beautiful star cluster in the entire heavens is 
located just about 18 northeast of Alpha Centauri. This 
globular cluster, known as Omega (co) Centauri, is a gorgeous 
object even with field glasses. It contains 5,000 stars, including 
over 130 variables; and according to Professor Shapley it is 
the nearest globular cluster, at a distance of 21,000 light years. 
If the sun were removed to that distance, it would appear as a 
star of the twelfth magnitude. 

East of Crux and near Centaurus is Circinus, the Compass, 
outlined by four stars. Alpha Circini is at the joint of the 
Compass, Beta and Gamma at the two points. Triangulum 
Australe, the Southern Triangle, is neighbor to the Compass. 
It is formed by one second and two third-magnitude stars. 



Stars of the Southern Skies 



33 



CRur 


a . 




f 
/ 


^ 


a 


% "Z.sry 




/ 


/ 


?' f K 


f / CIRCINUS 




/-^. *"> 

/ ^ XI 


PAVO / 


\ 4 


T 




^ INDUS / i 


V^* 


: ^ 


..-i 1 




/ .4 




4c; 


CENTAURUS -.. 




.* *-" 


, f *> 


"*^ 


^ t ..> 




r 


q 




""S ""^ 






\ % 
\ 



The faint constellation Norma, the Level, is just north 
of the Triangle; Apus, the Bird of Paradise, is south. Ara, the 
Altar, lies near the tail of the Scorpion and is composed mostly 
of third-magnitude stars. 

Now returning to the base of the exploring expedition, the 
Southern Cross, the journey will continue west. The constella- 
tion Carina, the Keel and Hull of the Ship, and Vela, the Sails, 
are due west of Crux. Carina has a surprising number of ruddy 
and variable stars. 

A great number of travelers to the south are confused by 
the False Cross, which is almost the exact replica of Crux 
although it is slightly larger. This False Cross is composed of 
Delta and Kappa Velorum and Epsilon and Iota (i) Carinae. 

Eta Carinae is an irregular variable star in the midst of a 
wonderful nebula. A glance at its remarkable history reveals 
that, although it was fourth magnitude in 1677, it rivaled 
Sirius in 1842. It later became invisible to the naked eye and 
is today a telescopic object of nearly eighth magnitude. 

About 90 west of the Southern Cross lies the second 
brightest star in the whole heavens Canopus, Alpha Carinae. 
Its magnitude is 0.9, and it is one of the very few super-giant 
stars. This extraordinary star shines with a white light slightly 
tinted with yellow, and although it is over 400 light years 
away it appears bright to us because it radiates about 45,000 
times as much light as the sun! 

Eighteen degrees nearly southwest of Canopus is the Great 
Magellanic Cloud (Nubecula Major) and about 70 due west 
of the Great Cloud is the Lesser Magellanic Cloud. The Greater 



Handbook of the Heavens 



V 


'"^N 




\ ; 
^ TOUCAN }} 






ARA * 




\ + 


1 




, r 




\ PHOENIX \ 




f\ 


\ J 




\ HYDROS 




1 1 


t \ TEIESCOP1UM 




ocm -^ 


\ 


f \ NO 


\ ,* 

DXXA V 'V 




< ; / '" \ ... 




1 \ 


CORONA 
AU5TRALIS 




^ ^ < 

ERIDANUS^/ ^-* 
/ *\ HOROL061UM 





Cloud is about 7 in diameter or fourteen times that of the 
full moon, and is situated on the border of Dorado, the Sword- 
fish, and Mensa, the Table Mountain. The Lesser Cloud, which 
is less than 4 in diameter, lies in Tucana, the Toucan. Their 
brightness, according to Sir John Herschel, "may be judged 
from the effect of strong moonlight, which totally obliterates 
the lesser, but not quite the greater." These great objects 
are ma'de up of star clusters and nebulae. One of the members 
of this cloud is the super-giant variable S Doradus which, at 
its maximum, is half a million times brighter than the sun. 
The actual diameter of this immense object is about sixty 
million miles and it is intrinsically the brightest object 
known. 

About the same distance from the south pole as Crux 
but on the opposite side of the heavens is the constellation 
Eridanus, the River Po, with its bright star Achernar. Eridanus 
flows in a long winding course from Rigel in Orion over 
to Cetus, past Fornax and Phoenix to Hydrus, ending in 
Achernar. The total length of this "Mississippi of the Sky" 
is about 130. The constellation is composed mostly of fourth- 
magnitude stars with Achernar standing out by virtue of its 
brilliance. 

Omicron (o) Eridani is a beautiful triple star in which 
the two faint companions are over 43 billion miles from their 
primary. In this region is located a planetary nebula described 
by Lalande as the most extraordinary object of its kind he 
had ever seen. It consists of an eleventh-magnitude star 
surrounded by a circular nebula, and this set against a larger, 



Stars of the Southern Skies 35 



*>* 

CHAMAELEON ^ 

j %.. ^ ^ TOUCAN 

^' ^ APUS!\ 

/ \ I** \ 

^ ^ X - f -" GRUS 

TRIANGULUM AUSTRALE ""*' 



hazy cloud. Gamma Eridani is a fine contrasting double star, 
magnitudes 2.5 and 10, separation 51 seconds. It is not in the 
circumpolar section, however. 

Eridanus is surrounded by nine constellations: Hydrus to 
the south; Phoenix, Fornax, and Cetus to the west; Taurus on 
the north; Orion, Lepus, Coelum, and Horologium on the east. 

In the southeast corner of Toucan lies the Lesser Magellanic 
Cloud, which is visible to the naked eye. Near by is the famous 
globular cluster, No. 47 Tucanae, whose 22,000 stars blend 
into a single star of the fourth magnitude when seen without 
optical aid. 

Directly south of this group is the constellation nearest 
the south celestial pole, Octans, the Octant. Sigma (d) Octantis, 
sixth-magnitude, may be called the Polaris of the south; it is 
just a little less than i from the true south celestial pole. 

Most of the names assigned to the constellations in this 
region of the heavens are of modern origin because the greater 
number of ancient astronomers lived in northern climes and 
few ever went south to continue their work. Among the com- 
paratively recently named constellations there appear Antlia, 
the Air Pump; Chamaeleon; Circinus, the Compass; Columba, 
the Dove; Crater, the Cup; Crux, the Cross; Fornax, the 
Furnace; Horologium, the Timepiece; Indus, the Indian; 
Mensa, the Table Mountain; Microscopium; Musca, the 
Fly; Pictor, the Easel; Pavo, the Peacock; Telescopium; 
and Volans, the Flying Fish. 

Within 40 of the south pole there are stars representing 
twenty-seven constellations, while in the same area around the 



36 Handbook of the Heavens 

northern pole only fifteen are represented. There are five 
first-magnitude stars in this southern area and none in the 
northern. The southern sky has about ten second-magnitude 
stars, the northern about thirteen. So from studying both 
northern and southern circumpolar skies it may be concluded 
that the south circumpolar sky has the more brilliant constella- 
tions and individual celestial objects. 

But when the heavens 50 south of the equator are com- 
pared with those 50 north, both sides come out just about 
even in brilliance and interest. In all, 6,000 stars are visible 
to the naked eye and they are shared almost equally by both 
hemispheres. 



Exploring among the Planets 

CIRCLING forever about the sun, the planets move against the 
background of constellations that form the zodiac. Day after 
day they speed on their way, each a fascinating world revealed 
to us only by reflected sunlight, for the planets are dark and 
cold and borrow their brilliant, steady light from the sun. 

Quickest of them all and closest to the sun is little Mercury, 
which completes a revolution its year in about eighty-eight 
days. With the same face always toward the sun because its 
rotation period is equal to that of its revolution, one-half of 
the planet is constantly scorched by the sun's rays while the 
other side is locked in the perpetual cold and blackness of an 
eternal night. However, owing to the constant rotation and 
the slightly varying orbital speed (because of its elliptical 
path), there is a fairly wide zone on Mercury along the twilight 
line where the sun alternately rises and sets. 

Even here the rugged surface is unprotected by an atmos- 
phere and as a result drastic changes minimize the possibilities 
of life on the planet. 

Because of its nearness to the far more brilliant sun it is 
on the average only 36 million miles distant this speeding 
little globe is seldom seen. There are six two-week periods 
during the year when it is well situated for observation. 
These occur at the times of greatest elongation, or when the 
planet is at its farthest distance from the sun as seen from 
the earth. At the time of greatest eastern elongation, Mercury 
sets soon after the sun and is seen in the west as the so-called 
" evening star." About two months later, reaching greatest 
western elongation, it will rise in the eastern sky soon before 
the sun and be known as the "morning star." 

Although visible only for an hour or so on each of the days 
near elongation, Mercury shines with a brightness which varies 
between that of Aldebaran and Sirius In a 2- or 3-inch tele- 

37 



Handbook of the Heavens 




Ytrkes Observatory 

VENUS. The planet Venus in cres- 
cent phase, as she appears to the great 
4O-inch refracting telescope at Yerkes. 
She shines most brilliantly at such times 
because of her nearness to the earth, 
although but a fraction of her illumi- 
nated surface is visible. It is when the 
planet is but a slim crescent that she is 
sometimes bright enough to cast a shadow. 



PHASES OF MERCURY AND FEN US 

1 Inferior conjunction 

2 and 2' Greatest brilliance 

3 Greatest elongation west 

(a morning star) 

4 and 4' Gibbous phase 

5 Superior conjunction 

6 Greatest elongation east 

(an evening star) 



scope, it appears as a pale yellow globe without surface detail, 
but it displays phases similar to those of the moon, the causes 
of which are shown in the diagram above. 

Yellowish-white Venus at her best is more than fifteen times 
as brilliant as Sirius, the brightest star in the heavens. She 
takes about 225 days for her journey about the sun, traveling 
along an orbit that is almost a perfect circle. Of all the planets, 
she is the one most nearly comparable to the earth, for her 
diameter of 7,575 miles is about equal to the earth's. 

Venus has been observed to have a very dense atmosphere 
which, however, contains practically no oxygen. It is possible, 
however, that what has been observed is merely an outer 
layer of atmosphere above a blanket of dense clouds which 
surround the body. This suggests the possibility of oxygen 
beneath the clouds sufficient to sustain life. 

Like Mercury, Venus is never very distant from the sun. 
For certain periods of time she is invisible to the naked eye, 
although her periods of invisibility are not so frequent as those 
of Mercury. She can be seen at the time of dawn or sunset, but 



Exploring among the Planets 39 

for no more than four hours at a time. However, Venus can 
at times be seen in daylight with the naked eye. 

Using a small telescope, we can watch Venus go through 
phases just like those of Mercury. When the planet is farthest 
from the earth, on the opposite side of the sun, she is "full"; 
when nearest the earth she is in crescent. The planet apparently 
changes in size as it goes from crescent to full and back to 
crescent, and its apparent diameter is six times as great in 
crescent as when it is full. At its maximum brilliance, which 
occurs 36 days before and after inferior conjunction, it is only 
a crescent. It is then plainly visible and sometimes even bright 
enough to cast a shadow. 

Little of the surface has ever been seen except under very 
fortunate and perhaps unique observing conditions. For this 
reason the rotation period or day of the planet has not yet 
been satisfactorily determined. 

Both Mercury and Venus are visible for the greatest lengths 
of time before sunrise and after sunset when they are at their 
greatest western and eastern elongations, respectively. The 
planets are brightest as they pass near the earth between the 
elongations. 

Traveling outward in the solar system, we pass the earth 
and arrive at the ruddy Mars, which because of its color has 
long been symbolic of the war god. It is only 4,230 miles in 
diameter the smallest planet in the solar system except for 
Mercury. 

Mars goes through seasons similar to the earth's because 
its axis is inclined to its orbit at an angle similar to that of 
the earth's. Its day, ^ 27 m , is also comparable with the 
earth's, but its year is nearly twice as long, for it takes 687 days 
to complete its journey around the sun. 

Aided by nearly perfect seeing conditions, several widely 
known observers of Mars have distinguished linear markings 
or " canals." At first they were attributed to the handiwork 
of an advanced race of human beings who dug them to bring 
water down from the poles, but this sensational idea has been 
more or less abandoned. Indeed, the best observers are quite 



Handbook of the Heavens 




Retrograde Motion of M^irs 
? Id net 




Ytrkes Observatory 



MARS. Prominent in this photo- 
graph of Mars is the south polar cap, 
which changes in size with the seasons. 
Syrtis Major, the wedge-shaped area 
extending toward the north, changes 
color to correspond with the variations 
in the polar cap and some astronomers 
say it is a vast area of vegetation. 



When the planets are in position 2, 
Mars appears to be moving normally as 
seen from the earth. But gradually the 
earth passes Mars and the red planet 
seems to move more slowly. In position 
3 it apparently starts to move backward 
and it continues so in 4 and 5. In 6 it 
once again moves forward. 



in disagreement as to whether the canals actually exist, for 
it is a question of seeing detail at the extreme limit of visibility. 

Easily picked up and observed when visible, Mars shows a 
reddish surface with grayish or greenish markings. Even with 
a small telescope some surface detail is visible. Because of 
the great transparency of the Martian atmosphere, the 
polar caps can generally be seen, except when they melt away 
during the long summer. The pole caps are believed to be 
either frozen water or carbon dioxide. Extensive reddish areas, 
the continents of the early observers, and green or gray regions 
or lakes are plainly visible with sufficient magnification. 

For Martian observations with a small instrument a 
magnification of 200 to 350 diameters is required before one 
begins to see surface detail; with magnification of 300, one 
begins to see polar caps, Syrtis Major, and other dark areas. 

The red planet is attended by two moons, Phobos and 
Deimos, neither more than 10 miles in diameter. They are so 
close to the planet and so small that they cannot be picked up 
with anything but the largest instruments. Phobos, the inner 



Exploring among the Planets 41 




B 

Aft. Wilson Observatory 

JUPITER. Ganymede, largest moon of Jupiter, throws its shadow on the belted surface 
of the planet just before the satellite itself crosses in transit. The shadow is more easily 
observed than the satellite which is soon lost on the planet's disk. 

moon, speeds about the planet in less than one-third of a 
Martian day and, interestingly enough, it rises in the west and 
sets in the east. 

Man has let his imagination run away with him in con- 
templating the possibility of life on Mars. Whether the canals, 
which some astronomers claim they have seen, are really 
waterways and whether Syrtis Major is really a vast area 
of. vegetation remain unanswered questions. And the ideas 
of writers which picture the Martian man as anything from a 
creature resembling an octopus to a highly intelligent being 
are never ending. 

Beyond Mars lie the diminutive asteroids, which are dis- 
cussed separately elsewhere, and outside this belt of minor 
planets is Jupiter, the largest planet in the sun's system. Pac- 
ing slowly and majestically through the heavens, this great 
cooled-off mass measures 82,880 miles from pole to pole. 
It is outshone only by Venus and occasionally by Mars and 
appears as a star much more brilliant than Sirius. 

The amateur with his small telescope sees on Jupiter 
soft shades of red, yellow, tan, and brown and a wealth of 
other telescopic detail. Exceptional sight is not required to 
get a clear view of the surface markings, and often a slight 
haze or smoke in the air will steady the image. Barring the 
belts which stretch in parallel lines across the disk, the chief 
marking is or was the much-talked-of "red spot" of Jupiter. 



42 Handbook of the Heavens 

First discovered on the Jovian surface in 1857, it has disap- 
peared and reappeared during the years. A curious feature of 
this floating beauty mark is that it leaves behind it a hollow 
space to mark its position each time it vanishes. 

Of Jupiter's nine moons, four are visible even in a field 
glass. Their positions in relation to the primary vary from 
night to night, and indeed from hour to hour. Readily identi- 
fied, they may be watched through many interesting hours 
as they speed in front of Jupiter, throwing their shadows on 
the planet, or vanish behind its giant disk or plunge suddenly 
into its immense shadow. With care, it is possible to follow 
the transits of their shadows, and to time their passages behind 
the planet. A record kept of the moons from night to night 
gives a graphic picture of their whirlwind paths about Jupiter. 

The system of Jupiter and its moons presents a miniature 
solar system, orderly and regular in manner. Each satellite 
has a definite period (which you may time for yourself and 
then check with an ephemeris); each has a definite path; 
each travels in a set direction about the planet. Of the five 
satellites that are not visible with small instruments, the 
outermost two revolve about Jupiter in retrograde direction 
from east to west. Discussion has arisen from this fact as to 
whether they might not be captured asteroids and therefore 
not originally members of Jupiter's system. 

Saturn, the next planet beyond Jupiter, was the last 
known to the ancients who were unequipped with telescopes. 
And without telescopes, these ancients missed the most 
wonderful sight to be found in the entire heavens. For Saturn, 
with his beautiful rings, deserves that title; it presents a 
magnificent spectacle. 

The ring, for it appears as a single flattened object in a 
small instrument, is poised high over the planet's equator, 
its inside edge about 7,000 miles above the cloud surface. At 
different times it appears to us inclined upward or downward 
and it may even disappear for a time, because, when it is 
viewed edge on, it actually is invisible. The rings are really 
inclined at an angle of 27 and remain that way always; but 



Exploring among the Planets 43 




Barnard at Yerkes Observatory 

SATURN. Saturn's rings, darkened in the rear by the planet's shadow, show up 
beautifully in this photograph. Cloud belt surface and Cassini division of the rings are 
defined. 

as the planet moves around the sun, we see them at varying 
angles from the front, the rear, or the side, according to 
Saturn's position with respect to the earth. 

Twice every thirty years Saturn reaches a place in its 
orbit where the rings are tilted edge-on to the earth. At this 
time they disappear when viewed with small telescopes and 
are seen only in the most powerful ones as a fine needle thrust 
through the globe. They are made visible at such times only 
by the sunlight passing through them. The rings reflect so 
much light that, when they present their broadsides to the 
earth, the planet appears three times brighter than when the 
rings are edgewise. 

A telescope shows the divisions of the rings clearly. First 
to be noticed is the Cassini division which divides the system 
in two, and \^hich is easily seen in a small telescope. Then on 
the outer ring we may see the faint, gray Encke division. This, 
however, is illusive and is not always visible. The inner ring 
gradually shades ^ff on the inner edge to meet the misty gray 
border, the crepe ring. 

The outline of the planet has been vaguely seen through the 
crepe and outer rings, and stars have been seen through all 
three, for they are composed of hundreds of tiny moonlets 
revolving about the planet. The rings throw their shadow 



44 Handbook of the Heavens 

on the surface of Saturn as a dark, sharply outlined band. 
In turn, Saturn throws its shadow across its belt of rings as a 
black shape outlining one rim of the planet. 

As for its surface, the ringed planet is somewhat like Jupiter 
in that it too seems spanned by cloud belts. Little of these can 
be seen, however, except under exceptionally fine conditions. 
Occasionally a spot mars the complexion of Saturn, a spot 
which is very useful in determining the precise rotation period 
of the planet. The latest one, discovered in 1933, was called 
the "white spot" and, although it has since diminished some- 
what, it is still faintly visible. 

Saturn, too, is blessed with nine moons and so outrivals 
Jupiter, equaling him in satellites and bettering him in rings. 
At one time, the planet was thought to possess ten moons, 
but the tenth has, since its reported discovery, vanished and 
there is some doubt about its existence. Without a more 
powerful instrument than a 3-inch telescope it is difficult to 
make observations of the satellites, although Titan frequently 
can be seen with such a glass. Care must be taken to distinguish 
them from the stars, but the moons Titan, lapetus, Rhea, 
Tethys, and Dione are supposed to be visible in a 4-inch 
telescope. They are named in the order of their observational 
possibilities. 

Discovered by Herschel in 1781, Uranus is the next planet 
in order out from the sun. About 30,000 miles in diameter, it 
can be seen as a sixth-magnitude "star" despite its 1,780 
million miles' mean distance from the sun. It can be seen as a 
naked-eye object by observers gifted with good eyesight. 

Through a telescope it appears as a tiny green body with 
vaguely defined belts stretching across its surface. No perma- 
nent markings have been perceived upon it that can be used 
for the exact determination of its rotation period, but this was 
spectroscopically determined by Slipher who found the period 
to be about 10% hours. 

Uranus has four satellites, but they are all very faint and 
cannot be observed except with large telescopes. The chief 
observations possible for amateurs are the locating of the 



Exploring among the Planets 45 

planet and the mapping of its path among the stars. With the 
aid of the charts published here, it may easily be followed. 

Neptune was not discovered until 1846, but it wasxnpt long 
afterwards that it was found to have one satellite. Although 
Neptune is larger than Uranus, with a diameter of 3 1,000 miles, 
Neptune's greater mean distance from the sun, 2,790 million 
miles, makes it quite invisible except in a telescope of 2 inches 
or greater aperture. It is, at its brightest, an object of eighth 
magnitude, and with a little care it may easily be located. 
Triton, its one satellite, is out of the reach of a small telescope, 
but with such an instrument you should make out the greenish 
color of the planet itself. Very much to be recommended is 
the reading of the " Hints on Telescope Usage" (page 94), 
which describes the proper technique for locating this planet 
and other telescopic objects. 

Completely out of the range of small instruments, and 
indeed not easy for a 1 5-inch refractor, is Pluto, found after 
years of search in January, 1930. It is so far distant from the 
sun that it takes 248 of our years to complete one revolution 
and consequently spends 20 years within the boundaries of 
one zodiacal constellation. It is still near its discovery point 
at Delta Geminorum. We know little more about it than that 
it is about one-half the size of the earth and has no satellites 
yet discovered. 

An excellent piece of naked-eye observation of any one of 
the planets is the mapping of its path among the stars. Sooner 
or later (except in the cases of Venus and Mercury which are 
invisible at such a time) the observer will notice the retrograde 
motion of the planet. That is when it seemingly turns around 
and backtracks along its former path. But before it has gone 
far it will turn again and proceed in its original direction. 
This is an interesting phenomenon and is an effect caused by 
the relative movements of the earth and the planet under 
observation. The diagram on page 40 shows this for the earth 
and Mars. In the following planet maps retrograde motion 
appears in the path of almost every planet during the period 
covered by the maps. 



Planet Maps 

In the following planet maps, the apparent path of each of 
the planets is indicated by a long curved line. The dates locate 
the position of the planet at different times during the year. 

To learn whether Venus, for instance, is a morning or 
evening star, refer to these maps to learn in which constellation 
it is located at the time. If the path is dashed in the maps of 
Mercury, Venus, and Mars, the planet is invisible. If it is 
visible, refer to the constellation maps to learn when and in 
what part of the sky the group containing the planet may be 
seen. 

The charts for Jupiter and Saturn show stars to the limit 
of naked-eye visibility. The charts for Uranus and Neptune 
show stars down to 93. Only the naked-eye stars are labeled 
on these two charts. Uranus is on the limit of naked-eye 
visibility and hence its magnitude is close to that of the three 
BD stars (see the Bonn Durchmusterung^ Argelander's great 
atlas and catalog of stars to declination 2). Neptune is 
much fainter, somewhat brighter than the fainter stars shown. 



4 6 



Planet Maps 



47 





Handbook of the Heavens 




Planet Maps 



49 




Handbook of the Heavens 



A Q U A R I U S 




Exploring on the Moon 

SLOWLY the sun rises over the barren, sandy wastes and the 
great jagged mountain peaks that form a conspicuous part of 
the moon's surface. Slowly it reveals to the patiently waiting 
astronomer the landmarks that make the moon the most 
interesting planetary object for amateur observation. The 
amateur astronomer finds that the moon's topography, studied 
even with a small telescope, field glass, or the unaided eye, 
is far more fascinating than the earth's. 

But, just as terrestrial geography is systematic, so is 
lunar topography, and to make a good beginning it is wise to 
learn the maria, or seas, so named by the early lunar observers. 
These great areas are really dark-colored and comparatively 
smooth plains. The first large one visible as the moon swings 
around the earth after its "new" phase, and one that is easily 
recognizable by its isolation, is Mare Crisium. As the moon 
waxes, the next to appear are, in order: Mare Foecunditatis, 
Mare Nectaris, Mare Tranquilitatis, and Mare Serenitatis. 
When all these are in view, the moon has reached its first 
quarter. 

It will then seem to grow to a full moon, become again a 
quarter, then a crescent, and finally disappear from view. 
To the observer of lunar surface markings the phases are 
significant because the best place to observe a lunar feature 
is at the time of sunrise or sunset on that object. It is then 
brought into sharp relief by the shadow it casts and is located 
on the terminator where sunlight ends and shadow begins. 
The terminator is constantly shifting across the moon with the 
changing phases. 

The diagram on page 53 illustrates these phases and their 
cause. The inner circle shows how the moon really is as it 
revolves around the earth; the outer circle, how the lighted 
half of the moon appears to us. The phase varies with the 

51 



52 Handbook of the Heavens 

angle from which we observe the parts of the moon lighted 
by the sun. At times a portion of the moon (not lighted by 
the sun) appears faintly illuminated. This is "earthshine" 
the light which the earth has reflected to the moon which 
makes visible, areas of the moon which would otherwise be 
dark and invisible. Sometimes in a clear atmosphere one 
can distinguish with the naked eye the seas lighted by earth- 
shine and with a telescope certain other of the major details. 

Nightly observations of the moon reveal that, on the 
average, it rises about 50 minutes later each evening. This is 
because the moon, in its monthly revolution around the earth, 
moves approximately 13 eastward through the zodiac in a 
day. As a result, should the moon rise at 10 P.M. on one evening 
it would still be below the horizon at the same time next night, 
and 50 minutes would have to elapse for the earth to rotate 
enough to allow the satellite to appear over the eastern horizon. 

Between first quarter and full moon Mare Vaporum, Mare 
Frigoris, Mare Imbrium, Mare Nubium, Mare Humorum, and 
lastly the great Oceanus Procellarum, the Ocean of Storms, 
appear. This last is the most easily visible to the naked eye. 

On the northwestern edge of Mare Tranquilitatis, near 
the Mare Crisium, will be found the Palus Somnii, the Marsh 
of a Dream. On the northern " shore" of Mare Imbrium will 
be found two promontories, Promontory Laplace and Prom- 
ontory Heraclides, enclosing the semicircular Sinus Iridum, 
the Bay of Rainbows. Some of the mountains bordering on 
this bay are said to have peaks towering to 20,000 feet. 

Connecting with the side of the Mare Imbrium is the Sinus 
Aestuum, the Bay of Hearts, and still farther soxith and 
almost in the center of the visible hemisphere of the moon 
is the appropriately named Sinus Medii. To the west of Mare 
Imbrium can be found the Palus Nebularum, the Marsh of 
Clouds, and the Palus Putredinus (between Imbrium and 
Serenitatis) . The inconspicuous Sinus Roris is north of Procel- 
larum and connects with Mare Frigoris. 

Once these maria, marshes, swamps, etc., have been 
discerned, it is natural for the telescopist to develop a strong 



Exploring on the Moon 



S3 




ex 



Gibbous 





Full moon 

Gibbous 

o c 




Earth 



Crescent 
Last quarter %/^ 





3 



Yerkes Observatory 

MOON. Near the sunrise line are the 7Y/ MOON'S PHASES. The inner 

lunar Apennines, brought into sharp circle represents the moon as it appears 

relief by the sun's slanting rays. Some from a point above the earth's pole; and 

of the towering peaks on the dark side the outer circle shows it as it is seen in the 

are tall enough to be seen while the sky (considered apart from the diagram), 
valley below is in darkness. 

interest regarding the circular, crater-like objects, which, next 
to the seas, are the most conspicuous objects to be observed on 
the moon. 

The largest of these crater-like formations are the "moun- 
tain-walled plains/' They range in size from 60 to 150 miles 
in diameter. These plains, which closely resemble smaller 
maria, are encircled by mountain masses of different heights. 
The interior is much depressed below the level outside the rim, 
this rim or rampart often rising but little above the sur- 
rounding land. Typical of these mountain-walled plains are 
Clavius (the largest), Schickard, Ptolemaeus, Maginus, and 
Grimaldi. All of these and numerous other objects appear on 
the moon map on page 59. 

The second group of crater-like features is the " mountain- 
ringed plains." The ramparts are practically circular, 10 to 
60 miles in diameter, with steep inner slopes and gentle 
outer slopes; the floors are deep depressions; many craters 
may be discovered on the tops of the walls or on the outer 
slopes; often there are central peaks: Theophilus, Aristillus, 
Aristoteles are typical of these. Copernicus and Tycho also 
belong here and are noted for the striking ray systems radiat- 



54 Handbook of the Heavens 

ing from each, these being seen best at the time of full moon. 
The rays from Tycho extend for hundreds of miles over moun- 
tain and plain without interruption. Plato is unique in color 
and easily located. It was in this crater that Pickering dis- 
covered monthly variation, which he supposes is caused 
by vegetation. Herschel is a small ringed plain north of 
Ptolemaeus. When on the terminator it can easily be dis- 
cerned with eighteen-power binoculars and is a beautiful 
sight, small and round with a very bright inner wall. It 
thus makes a fine test for low magnification. 

The third type consists of the " craters" or " crater rings." 
These craters proper are but 3 to 10 miles across and are too 
small to be picked up with low telescopic power. They are 
almost perfectly circular, very numerous, and of much interest 
to observers with telescopes using 50 to 500 diameters. They 
are too small to be indicated on the lunar chart, which shows 
only the larger and more easily observable objects. 

Of the mountain ranges, the more striking ones are named 
after terrestrial ranges; for instance, the Alps, Apennines, and 
Carpathians, all of which are part of the irregular border of 
Mare Imbrium. In these lunar ranges are many hundreds 
of peaks whose elevations average over 10,000 feet. Some rise 
higher; Mt. Huygens in the Apennines and Mt. Hadley in 
the Palus Putredinus rise to heights of 15,000 to 18,000 feet. 
The Leibnitz range is the highest on the visible lunar surface 
and some of its peaks are perhaps higher than Mt. Everest, a 
few being said to attain 30,000 feet. The range is located on 
the extreme southern limb and so it is seen only in profile. 
All these ranges resemble earthly mountains, although erosion 
is commonly supposed to be quite absent; this may not be 
true, however, as the Riphaen mountains (for example) 
appear to have suffered much erosion. 

The crater Aristarchus is notable as being the brightest 
object on the moon and by early observers it was often 
mistaken for an active volcano. The deepest depression to 
be seen is the small crater Newton. The Straight Wall is a 
strange object and not very difficult to pick up. When the 



Exploring on the Moon 




Yerkes Observatory 

OCCULTATION OF ALDEBARAN. At the left, the star is seen just before it dis- 
appears behind the dark limb of the moon. The second picture was made just as it was mov- 
ing from behind the moon, on the lighted limb, and the third plate was exposed less than 
two minutes after the star had completely emerged from behind the satellite. The panel is 
arranged to present the phenomenon as it appears to the naked eye, 

light is right there is a bright edge with a narrow black border. 
It is believed to be a "fault" and is located in the south- 
western corner of Mare Nubium. Look also for the Straight 
Range between Plato and the Promontory Laplace. This 
formation assumes a nearly uniform, straight line, east and 
west, about 45 miles long, with at least a dozen peaks dis- 
cernible with high enough magnification. The central peaks in 
many of the craters and crater-like objects have been success- 
fully used to account for the lunar formations in both the 
volcanic and meteoric theories of the moon's origin. 

There is no end of interesting material for moon explora- 
tions, because more advanced work in observing, besides 
touching the foregoing types, also brings in isolated mountains, 
dome-shaped hills, crater chains, crater pits, rills, many twin 
craters, multiple craters, ruined ring plains, hilltop craters, and 
other special formations. 

In addition to presenting many features of interest in its 
topography, the moon plays an important part in several 
spectacular celestial phenomena. Chief among these are 
occultations and eclipses. 

As the moon moves through the sky, it frequently glides 
in front of a star or planet, blotting it from view. Since the 



56 Handbook of the Heavens 

moon always moves eastward in the sky, the object always 
disappears behind the eastern edge and reappears on the 
western limb. In an occultation, as it is called, of a star below 
fourth magnitude a telescope is usually necessary because the 
moon's light cuts the star from naked-eye view before its 
disk actually eclipses it. And it must be remembered that an 
astronomical telescope reverses the object. Therefore a star 
which, to the naked eye, appears to the left of the moon will 
seem to be at the right in the telescope. 

The most interesting effect is when the dark side of the 
moon is in the lead (any time before full) and the star dis- 
appears without warning. Another unusual sight is the occulta- 
tion of a double star. 

The disappearance of the star in an occultation is instan- 
taneous because of the fact that there is no atmosphere on 
the moon and because even the brightest stars appear and 
disappear as mere points of light. The abruptness of these 
disappearances and reappearances is indeed startling. 

The exact place of the moon in the sky can be determined 
and a knowledge of its motion refined by observations of 
occultations. It is essential that they be accurately timed if 
the observation is to be used for this purpose. Of course, it 
is much more difficult to predict them than to observe or time 
them. This takes almost an expert but amateurs can do it. 

The sight of the moon cutting off the light of a distant 
star is, however, less spectacular than that of the moon itself 
dropping from sight in the shadow of the earth. For, as the 
satellite swings about in its orbit, reflecting the sun's light, 
it must pass behind the earth and will occasionally be eclipsed. 

Usually it passes above or below the earth's shadow, but 
sometimes it does not. And then, with the sun's light shut off, 
it turns a dull red and becomes nearly invisible. This occur- 
rence, an eclipse of the moon, is illustrated by the diagram on 
the following page. 

In actual observation of a lunar eclipse, even in the midst 
of totality, it is noted that the moon does not really disappear 
but only dims and changes color. For even when the moon is 



Exploring on the Moon 57 




N x t ,Moon eclipsing sun 



/ s -T--^ 

"Moon eclipsed by earth's shadow 




in the midst of the earth's shadow, it does not lose all of the 
sun's light because some of it is refracted (bent) by the earth's 
atmosphere. Red, orange, and yellow light pass through the 
atmosphere most easily and for this reason the moon appears 
a copper color during the eclipse. 

It can be readily seen by the diagrams that eclipses of 
the moon, when they take place, are visible over half the earth 
at one time, while eclipses of the sun are visible only in small 
areas. For this reason, even though eclipses of the sun are 
more numerous, an observer at a given spot on the earth 
would see lunar eclipses more frequently than those of the 
sun. Furthermore he would see the moon eclipsed for a longer 
time. The moon, therefore, plays a part in two of the most 
interesting phenomena of the skies. 




MARE IMBRIUM REGION 

photographs yet made, this beauti 
" " " It is keyed for study. 



Mi. Wilson Observatory 

OF THE MOON. A portion of one of the finest moon 
ful picture shows Mare Imbrium one of the so-called 



I Plato 


14 Carlini 


27 Timocharis 


2 Pico 


15 C. Herschel 


28 Archimedes 


3 Condamine 


1 6 La hi re 


29 Autolychus 


4 Maupertius 


17 Lambert 


30 Aristillus 


5 Bianchini 


18 Euler 


31 Thaetetus 


6 Bouguer 


19 Pytheas 


32 Cassini 


7 Foucault 


20 Gay Lussac 


33 Piton 


8 Harpalus 


21 Eratosthenes 


34 P. Smyth 


9 Sharp 


22 Wolf 


35 Mt. Blanc 


10 Louville 


23 Mt. Huygens 


36 Kirch 


ii Mairan 


24 Mt. Bradley 


A Teneriffe Mts. 


12 Leverrier 


25 Conon 


B Straight Range 


13 Helicon 


26 Mt. Hadley 


C Prom. Laplace 



D Sinus Iridum * 

E Prom. Heraclides 

F Carpathian Mts. 
G Apennines 
H Palus Putredinus 

I Caucasus Mts. 

J Palus Nebularum 
K Alps 

L Alpine Valley 
M Sinus Roris 
N System of clefts southwest 

of Archimedes 
O Rays extending from 
Copernicus 



Meteors and Meteor Showers 61 





YerkfS Observatory 

METEOR TRAIL. An errant me- METEOR RADIANT. The paths 

teor glides into the star field of a Barnard of meteors belonging to a swarm trace 

photograph. backward to a common center. 



Composed of stone or metal or a combination of the two, 
the average meteor probably revolves in an orbit within the 
solar system and is subject to the gravitational attractions of 
any large bodies which it may approach. 

Many are found in groups which follow nearly regular: 
orbits around the sun. A few of these orbits may be identified 
as belonging to comets which may no longer exist. It is thought 
that these meteors are simply the remnants of the comet which 
has broken up or which is in the process of breaking up. 

The debris from the disintegrating comet becomes scattered 
around its orbit, and when the earth happens to cross one of 
these orbits, as it frequently does, many more meteors plunge 
into the atmosphere than do usually. If a large number of 
meteors are gathered into a central swarm traveling around 
the sun in the comet's orbit, and the earth intersects this 
swarm, the meteors can then be counted by the thousands. 

This explains the periodic meteor showers and it explains 
the strange periodicity of the Leonid shower, to take a definite 
example. Every thirty-three years a big shower is seen, and 
the display in 1833, previously mentioned, belongs to this 
group. This unusual shower which greets the earth three times 
a century occurs when this planet cuts into the main swarm. 
During intermediate years the earth swings through the 
meteor orbit without meeting the main condensation, but, 



62 Handbook of the Heavens 

nevertheless, hundreds of stray meteors are caught. In some 
cases, like that of the Perseids, the bodies have become well 
distributed about the orbit so that one year is about as good as 
another. 

Recently the Leonids have been very disappointing to 
amateur and professional astronomers who were expecting 
great displays. Meteor authorities attribute this disappoint- 
ment to the fact that Jupiter may have drawn the Leonid 
swarm away from its former orbit so that the earth does not 
cut through the densest part at the same time it did formerly. 

Of course, the best nights on which to watch for meteors 
are nights on which showers are due, for at these times it 
may happen that as many as 500 meteors are seen by one 
observer between midnight and dawn. During a shower the 
meteors seem to radiate from some particular constellation, 
and this point is called the radiant. Usually the shower takes 
its name from the name of the constellation in which its 
radiant is located. 

This radiant point is only an illusion, and the meteors 
have absolutely no connection with the constellation from 
which they appear to emanate. This is brought home by the 
fact that the star group which marks the radiant may be fifty 
light years away, while the meteors themselves, when seen, 
are only some fifty miles distant. The illusion of the radiant 
is caused by the fact that when parallel lines are extended 
they appear to converge. It is the familiar effect of railroad 
tracks converging in the distance. Since meteors travel in 
more or less parallel paths through the atmosphere, the effect 
is similar. 

Amateurs will find much pleasure and enjoyment in observ- 
ing and recording meteors any night during the year and can 
be of material assistance to the science of astronomy. Even 
the record of a single meteor may prove valuable when com- 
bined with the reports received from other observers in the 
region. And the apparently unimportant results of a night's 
observation may become extremely significant to an expert 
who can compare them with other reports. 



Meteors and Meteor Showers 63 

If only one person is observing, it is best to use a star chart 
and plot the path of shooting stars on it, together with a note 
of the time, as in the diagram on page 61. When this is done 
it may be noticed that some of the paths, traced backwards, 
will indicate a common point of origin. If two people are 
observing, it is suggested that one person observe and the other 
record the observations. In this way a constant watch is kept 
on the sky and no meteors are likely to escape attention. 

When more than one person observes the same sky area 
during the same time, care should be taken not to combine 
totals, as the unit used in recording and computing meteor 
falls is the number seen by one observer per hour. If possible, 
each meteor should be timed separately; otherwise the number 
seen every five minutes will do. 

When measuring paths, trails, or positions of particularly 
bright meteors, astronomers use the unit of i. The distance 
from the true horizon to the zenith is 90; it is 5 between the 
pointers of the Big Dipper; the belt of Orion has a length of 3. 
These dimensions can be used to judge other distances. 

In estimating the magnitude of a meteor it is best to com- 
pare its brightness with that of familiar stars. Capella and 
Rigel are of the first magnitude; Polaris is a second-magnitude 
star; the stars in the constellation Delphinus are of the third 
and fourth magnitude. 

The following chart is a suggestion made to expedite the 
recording of the meteors whether a shower is being observed 
or whether it is just an average night's fall. 

The observer should be warned that only on the nights 
indicated by asterisks are there actual showers, when large 
numbers of meteors may be expected. The unstarred nights 
have been reported as favorable by a large number of observers, 
and the meteors seem to show some relation to the radiant 
indicated. However, in the present state of knowledge, it is 
impossible to prepare a complete list of radiants and showers. 

Much research is being done on this problem and a large 
number of careful observations are necessary to solve it. The 
American Meteor Society, Upper Darby, Pennsylvania, will 
give specific directions to those wishing to make observations. 



6 4 

Name 



Handbook of the Heavens 

Date 



Sky 





Seen 










Time 




Speed 


Color 


Magni- 
tude 


Remarks 








First 


Last 










12:50 


Regulus 


Horizon 


Fast 


White 


I 


Trail 7, lasted 2 sec. 


12:53 


7 Leonis 


Spica 


Slow 


Yellow 


2 


No trail 


12:59 


6 Leonis 


Polaris 


Fast 


White 


I 


Trail, lasted 3 sec. 



CALENDAR OF GOOD NIGHTS FOR OBSERVATION f 



Date 


Shower 


Remarks 


June September 


7 Draconids 
a Capricornids 
a-0 Perseids 
5 Aquarids 
Perseids 
a Aurigids 
K Cygnids 
o Draconids 
Draconids 
e Perseids 
Quadrantids 
e Arietids 

(head of Draco) 
Orionids 
e Taurids 
e Taurids 
Leonids 

Andromedids 

Geminids 
Quadrantids 
K Cygnids 
a Aurigids 
f Bootids 
Lyrids 
7 Aquarids 
f Herculids 
tl Pegasids 
a Scorpiids 
t Draconids 


Slow; with trains 
Very slow; bright 
Swift; streaks 
Long paths; slow 
Famous shower; swift 
Very swift 
Medium 
Very slow 
Bright 
Swift 
Slow 
This shower is scheduled to return 
in 1940 
Very slow; fireballs 
Swift 
Slow; fireballs 
Very slow, bright 
Famous shower every 33 years 
but disappearing 
Famous shower disappeared in re- 
cent years. Slow, Biela's Comet 
Fine shower; white 
Good; medium speed 
Slow; trains 
Very slow; fireballs 
Swift; streaks 
Swift; streaks 
Very swift; long paths before sunrise 
Swift; white 
Very swift; streaks 
Very slow; fireballs 
Very slow 


Tulv 1 8^0 


Tulv 2C Aug. d. 


*Tulv 2C 10 


*Aug. 1012 


Aug. 12-Oct. 2 


Aug. 10-20 


Aug 2123 


Aug. 21-31 


Scot. 7i ; 


Oct. 2 


*0ct. Q 


Oct. 12-23 


*0ct. 18-20 


Oct. 3O-Nov. 17 


Nov. 3 i c 


*Nov. 13-15 


Nov. 1727 


*Dec. 10-12 


*Tan. 2-1 


Jan. 17 


Feb. 5-10 


Mar. 10 12 


*Apr. 20-22 


*May 6 


May 1 1-24 


May 30 


June 2-17 


June 27-30 





* The best showers. t Adapted from Norton with modifications approved by Dr, C, P. Olivier. 



Comets 

ALTHOUGH thousands of comets revolve in regular orbits 
around the sun, it is seldom that one becomes visible to the 
naked eye. However, nearly always there is one within reach 
of observers using a small telescope. 

When, from time to time, one of these space wanderers 
does mushroom into sight, it may grow brighter than Venus 
and even become visible in the daytime despite the over- 
whelming brilliance of the sun. 

Although tremendous in size, comets are really collections 
of small particles of matter so widely scattered that stars 
may be seen through thousands of miles of comet material. 
The nucleus, when present, is the densest part of the comet 
and is a meteoric mass at the central part of the head. Envelop- 
ing the head and visible in all comets is the coma, a faintly 
luminous gas cloud which often sends out a series of concentric 
shells or "envelopes." 

The coma is a large mass, nearly synonymous with the 
head, and the matter it sends out either as envelopes or as 
plain material seems to move steadily toward the sun. When 
it reaches a certain limit it seems to be repulsed by the sun, 
and it is then thrown back to form the tail. This is the most 
spectacular feature of naked-eye comets, although some do 
not have tails. When present, the tails always stream out into 
space away from the sun. Tail, head, and coma are generally 
composed of hydrogen, hydrocarbons, sodium, and other 
metallic vapors, together with fine solid materials. 

The average diameter of comet heads varies from 10,000 to 
100,000 miles, while the range in the length of tails in naked- 
eye comets is from 5 million to 200 million miles. The tail is 
shaped somewhat like a horn, and consequently it may be 
millions of miles wide at its end. 

Comets differ more in brightness than do any other celestial 
bodies. Some have been second in brightness only to the sun 

65 



66 Handbook of the Heavens 

and moon, while others are barely seen with powerful tele- 
scopes, and there are some that are so dim as to be beyond 
visibility. 

Comets are often discovered by astronomers who con- 
tinually sweep the skies with their telescopes searching for 
them. Among these comet seekers are numerous amateurs 
who add considerably to the total. Many new comets also 
have been found in recent years by photography. A comet is 
usually identified only after hours spent in visual or photo- 
graphic observation of its motion. 

When an observer comes upon a diffuse object in the field 
of the telescope, he should first refer to a reliable atlas to 
eliminate the possibility of its being a nebula or cluster. If 
it is comparable in brightness with average Messier objects 
in the surrounding field, the chances are that it is a comet. 
He should then plot its position with extreme accuracy and 
telegraph the Harvard Observatory, briefly stating its exact 
location and appearance. This will assure him of priority of 
discovery in the event that it is a comet. However, if it is 
possible to get in touch with an observatory or with an expert 
who has a list of current comets, it might be best to do this 
first before telling Harvard. 

Perhaps for his first adventure in comet hunting the 
observer would prefer to feel more sure of himself before 
notifying the observatory. If this is the case, he may discover 
some displacement of the object from the original position 
by observing it on subsequent evenings. The evidence of any 
motion in relation to the neighboring stars leaves little doubt 
that it is a cometary object of which the observatory 'should 
be notified. 

Of course, this may be a known comet for which he cannot 
claim the credit of discovery, but he will at least have experi- 
enced the thrill of discovering it for himself. 

Unusually brilliant comets are frequently given the name 
of their discoverers, as, for instance, Donati's Comet. A comet 
is also technically designated by the year in which it is dis- 
covered, followed by an a if it is the first to be found in a 



Comets 





Mt. Wilson Observatory 

II ALLEY 1 S COMET. Halley's 
Comet photographed during its visit 
to the earth in 1910. One of the most 
spectacular of the naked-eye comets, 
and the last great comet to be seen to 
date, it will not be visible again until 
1986. 



COMET DEBRIS. As a comet dis- 
integrates, it leaves behind it widely 
scattered meteoric material which con- 
tinues to follow the comet orbit. 
When the earth meets such a swarm, we 
have a " meteor shower." 



given year, a b if it is the second discovered, etc. Another 
method of classification is the year followed by a Roman 
numeral giving the order of perihelion (point nearest to the 
sun) passage, as Comet 1816 II. Both designations are used, 
the latter being applied after all the year's comets' perihelion 
passages have become known, while at first only the order 
of discovery can be used. 

Comets travel in three types of orbits: elliptical, parabolic, 
and hyperbolic. Those which follow hyperbolic and parabolic 
orbits will never again swing around the sun, once they have 
made this curve. Instead they continue on and on, far out 
beyond the solar system. 

But those whose orbits take the shape of ellipses do revolve 
about the sun in periods that vary according to the individual 
comet. About fifty are known to have periods of less than 



68 Handbook of the Heavens 

100 years, while some are thought to take 10,000 years to 
complete one revolution. The Comet 1864 II had a period of 
2,800,000 years and its aphelion distance was 40,000 astro- 
nomical units, or 3,720 trillion miles. 

Short-period comets are those which have periods of just 
a few years, and of these thirty-six complete a revolution in 
from five to seven and one-half years. They form a definite 
group, all moving in similar orbits, all being quite faint, 
and most of them having no tails. The aphelion (farthest 
distance from the sun) of each of these comets is very near 
to the orbit of Jupiter, and so it has been suggested that these 
comets, formerly traveling in parabolic orbits, were drawn 
into their present paths by Jupiter's gravitational attraction. 

Most comets move just as they would be expected to in 
free space under the laws of gravitation, but there is one 
striking exception. This is Encke's Comet, which has the 
shortest * period known 3.3 years. The period of Encke's 
Comet is observed to be shortening steadily, and this phe- 
nomenon is difficult to explain. It is believed that the comet 
meets with some unknown resistance in its path. This resist- 
ance causes a greater relative gravitational effect from the 
sun, and so the comet falls toward the latter more, shortening 
the orbital path and therefore its period of revolution. 

The long-period comets show little evidence of having been 
captured by any of the planets. They are often of great bril- 
liance, while those of shorter period are usually very faint. 



Double Stars 

Two tiny points of brilliant light, one a rich gold and the 
other a deep blue, glowing in a field of coal-black sky the 
double star Albireo, seen through a 3-inch telescope! 

It can be seen with a field glass or a small telescope, and 
it leaves an impression on the memory as clear as that left 
on a photographic plate. Albireo is the star Beta Cygni, the 
fourth brightest star in the constellation of the Northern 
Cross, which begins to rise in early May evenings. 

Albireo is only one of thousands of stars of its type which 
stud the heavens, their concealed beauties unsuspected until 
they are viewed with the telescope. These thousands of 
" double stars/' as they are called, are for the most part 
binary systems. That is, they are two stars which, although 
not actually in contact, have a physical connection with each 
other, for they rotate about a common center of gravity. 
Albireo is thought to be such a system. 

But there is another variety of double star in which the 
components are not connected but are simply so situated along 
the line of sight that they appear to be together, although 
one may be hundreds of light years behind the other. These 
stars must usually be within a half minute of arc of each other 
to be considered as "optical doubles." 

Then, too, there are the " naked-eye doubles" which seem 
to the unaided eye to be very close together but which generally 
have no physical connection. Of these Mizar (Zeta Ursae 
Majoris) and its near neighbor Alcor in the Big Dipper are 
the most famous. As they are brought under the telescope, 
one of the pair suddenly becomes a double in its own right, 
so that three stars appear in the field. Other naked-eye doubles 
include Alpha Capricorni and Epsilon Lyrae. 

As previously mentioned, the majority of the twenty 
thousand or so close visual doubles actually revolve about 

69 



70 Handbook of the Heavens 

a common center of gravity and are called physical doubles. 
Some of these binary systems have periods of revolution of 
five to ten years, although many of them have far longer 
periods. The motion as we see them from the earth are in some 
cases so slow that it takes centuries to establish an orbit. 
Until comparatively recent times, all double stars were 
thought to be composed of two stars that were nearly in the 
observer's line of sight. 

It was Sir William Herschel who accidentally stumbled upon 
the fact that in most cases the two stars actually do revolve 
around each other. He had, in 1789, turned his telescope to 
the task of observing a double with the intention of measuring 
the distance between the brighter star and the supposedly 
far more distant dimmer one. Instead, he made a new dis- 
covery that in most cases components of a double star 
actually revolve about each other, or rather about a common 
center of' gravity. Herschel's catalogues contain about 700 
double stars, including many important binary systems. 

The photographs on page 73, taken over a period of twelve 
years, clearly demonstrate this discovery of Herschel's. In 
them is shown the rotation of the two components of the binary 
Kriiger 60. 

The discovery of new double stars is made by simple 
telescopic observation, a departure from the usual lines of 
research. Professional hunters of doubles find that they need 
suitable atmospheric conditions, a trained eye, a telescope 
of good optical quality and large aperture, and a micrometer. 
The Lick 36-inch refractor, used in a recent search through a 
limited portion of the sky, revealed more than 4,300 new 
pairs. Work now in progress in the southern skies is expected 
to disclose thousands more. 

Yellow and purple, a magnificent combination of colors 
seen at its best in the natural setting of the stars, form the 
scheme of the star Eta Cassiopeiae, a double that can be 
found without difficulty. Also among the circumpolar star 
groups are the previously mentioned Mizar and Alcor, which 
appear as double to the naked eye and triple in a telescope. 



Double Stars 



Telescopic 


View 


Qt+ ^x-~~"~ 


""s^ 


/ 


, \ 


*. -* <' * 


t \ 


CYGNUS "* / ' * ; 


\ 

\ 

1 


f \ . ' 


7 


^-*- \ . 




/ x ' x x 


' 


j i/a Albireo s ^ 


s 


\ /' " "" 






Binary System 



But this three-star view approaches no limit, for deep in 
the Nebula of Orion is imbedded a jewel among star sights, 
Theta, a quadruple whose components form the Trapezium. 
Its stars, ranging in magnitude from 4.7 to 8, are white, lilac, 
garnet, and reddish. Although this quartet can be observed 
with a 3-inch glass, a larger glass reveals it in even more 
splendor, and more stars can be seen (see Orion, page 81). 

It might be well to mention that there is, so far as we know, 
no relation between double stars and star clusters. The cluster 
is by no means a further development of the double and 
multiple stars which we have been considering, for a cluster 
is a grouping of a considerable number of individual stars 
which may be in themselves single or double. 

In many cases, the component stars of a binary system are 
so close to each other that the most powerful telescopes in 
the world today cannot separate them. It is only when they 
are subjected to the searching eye of the spectroscope, astron- 
omy's second greatest weapon, that they are revealed. 

When a star is racing toward the earth, the lines of its 
spectrum as seen in the spectroscope are displaced toward 
the violet end of the spectrum; and when it is speeding away, 
the lines are displaced toward the red. If the spectrum of a 
star shows that some of the lines are displaced toward the 
red, while others are moved toward the violet, then we know 
that there are in reality two stars moving in opposite directions. 
This telltale split spectrum is a sure sign of a close double, 
and, as they are known to be twin stars only because of the 
spectroscope, this type is known as the " spectroscopic binary." 



72 Handbook of the Heavens 

Should the orbital plane of the pair be at right angles to 
the line of sight, so that neither of the stars appears to be 
moving toward or away from the earth, the spectroscope is 
unable to detect their motion, and doubtless many doubles 
under such a condition are still awaiting discovery. If the 
orbital plane of the pair passes through the earth, the two stars 
will eclipse one another, and they are known as eclipsing 
binaries. Such stars are often variable; see the chapter on 
"Variable Stars" (page 88). 

The great range of colors may best be shown by scanning 
the following list. Yellow and blue, orange and emerald, topaz 
and green are only a few of the descriptive comments you see; 

A SELECTED LIST OF BEAUTIFUL DOUBLES 



Double star 


Magni- 
tude 


Separa- 
tion, 
seconds 


Remarks 


f Ursae Majoris 
v Draconis 


2- 4 

c c 


H 

62 


Mizar 
A beautiful object 


6 Cephei . 


1 6 7 C 


4.1 


Yellow and blue (variable) 


y Andromedae 


2 A.- C 


IO 


Orange* greenish blue 


ct Capricorn! ... 


-J A 


176 


Telescopic double-double 


T Leonis 


$ 4.- 7 


QO 


Contrasting colors 


y Leporis 


18-64. 


QC 


Yellow and garnet 


6 Orionis 


2 c 6 o 


?1 


\Vhite and violet 


e Pegasi 


2 q- 8 c 


118 


Yellow and violet 


17 Persei 


1 Q- 8 ; 


28 


White and blue 


8 Cyeni 


1.2- C 4. 




Gold and blue 


f Lyrae ... 


4. 7 c Q 


4.4. 


Topaz and green 


c Lyrae 


r r 


2O7 


Double-double with high power 


y Virginis 


1717 


6 


Both yellow* easy 


y Arietis 


4. . 2 4. 4. 


8 


Good test for small glass 


77 Cassiopeiae ... ... 


17-76 


6 


Yellow and purple 


tx Geminorum 


2 1 


6 


Both white 


y Delphini . 


A C C C 


IO 


Yellow and bluish green 


e Bootis 


1-61 


i 


Orange and green* superb 


a Canurn Venaticorum 


1 2 C 7 


20 


Beautiful pair 


Serpentis ... 


A A 2 


22 


Both yellow* very fine 


55 Piscium 


q- 8 2 


6 


Yellow red or purple 


<t> Tauri 


c- 8 


C1 


Red and blue 


f Coronae 


4. I c 


6 


\Vhite* greenish 


5 Corvi 


1- 8 c 


24. 


Yellow and purple 


Aquarii 


4.- 4. I 


1 


Easy though close 


CL Tauri 


I-II 2 


16 


Fine in 4-inch telescope 











Double Stars 



73 



1908 



1915 



1920 



Ytrkes Observatory 

DOUBLE STAR KRUGER 60. Far out in the depth of space two stars swing about 
each other and photographer Barnard, at Yerkes Observatory, captures them on his 
plates. The pictures prove beyond all doubt the rotation of this binary star. 

and when one of these pairs bursts upon your field of vision, 
it finds you totally unprepared for the sight. 

Experienced observers find that the clearest nights, when 
the stars are twinkling excessively, are not the best times for 
seeing doubles; a calm night with a tranquil atmosphere, not 
disturbed by wind and layers of air of unequal density and 
often with something of a mist or haze, helps to keep the 
stellar image motionless. 

A highly corrected telescope objective or a reflecting 
telescope mirror will show the colors to best advantage in 
resolving stars. It is advisable to use the lowest magnification 
that will resolve the stars at the time. Those of very wide 
separation can be split with field glasses. Some, like Epsilon 
Lyrae, are double with low power and quadruple with high. 

Certain doubles are remarkably beautiful and can be 
profitably used as special ones for demonstration to new 
groups of enthusiasts. Such are Albireo, Castor, Gamma 
Andromedae, Epsilon Bootis, and Epsilon Lyrae. They vary 
in magnification needed, Albireo using 18 diameters, Epsilon 
Bootis 150. 

The foregoing list is but a suggestion; the heavens con- 
taining a vast wealth of material to use any clear night of 
the year starry gems that can be revealed only by a good 
telescope and careful observing. 



Solar Observations 

WHAT would happen if the sun suddenly ceased to shine, 
or if it changed its position in relation to the earth, or if it 
suddenly blazed up to many times its present light and 
heat? 

The results are too horrible to contemplate, but certainly 
an object that plays so important a part in our lives as does 
the sun is worthy of a good deal of observation and study. 

If you should turn a 2- or 3-inch telescope, carefully 
equipped with a darkened lens, upon the sun almost any 
day within the next few years, you might see a few sunspots 
scattered upon its bright yellow surface between 5 and 40 
north and south latitude. They are often grouped in pairs 
and clusters and seem to move across the disk as the sun 
turns on its axis. Some last during a full rotation (25 days); 
a few stay longer, but most have only a few days' existence. 

On careful examination these spots would be seen to con- 
sist of a dark center surrounded by a lighter area. Although 
they look so tiny in a small telescope, many of them are really 
large enough to engulf the earth, and some have been known 
to reach the size of 150,000 miles in diameter. Another strange 
thing about these spots is that they appear black when in 
reality they are white hot. 

When one turns a telescope on the sun, one does not always 
see only full-grown spots, for new magnetic storms are whirling 
up on the sun as old ones die down. New sunspots may first 
be detected in the process of formation as small black patches 
on the visible disk of the sun; or they may start to form on the 
side that is turned away from the earth, and then they will 
first be noticed as they round the edge of the sun. In this 
case they are marked by the bright patches called "faculae" 
which surround them. The faculae are seen best on the limb 

74 



Solar Observations 75 

of the sun, and they can rarely be seen at the center of the 
sun's disk. 

There are two general methods of observing these spots 
with the help of a telescope. One is by observing directly 
through the telescope, but extreme care must be taken to use 
a sun glass or ray filter. 

A second way is by allowing the enlarged image to fall 
on a piece of paper held at the eye end of the telescope. Rack 
out the eyepiece a little farther than for normal visual observa- 
tion. Then move the paper until the image is well projected 
and sharp. A wire frame can be made to hold it at the correct 
distance (see page 95). This leaves you free to chart the 
position of the spots by tracing them as they appear on the 
paper. It is a good idea to place a black cloth over the wire 
framework to keep out some of the extraneous light and thus 
make the image more distinct. A piece of cardboard with a 
hole in the center, placed on the telescope tube near the 
rack and pinion, also helps to keep out light. The advantages 
of this method are that it eliminates danger to the eyes, per- 
mits simultaneous observation by a number of observers, and 
facilitates charting. 

And, lastly, some people use a solar eyepiece, equipped 
with a prism that diverts most of the sunlight and permits a 
direct view of the sun with the least chance of danger to the 
eyes. But even with this "Herschel solar prism" a colored 
sun glass is needed. 

At times with even a 2-inch telescope, faculae may be seen 
in association with the spots. These are lighter areas above 
the sun's surface, which become more easily visible the nearer 
they are to the sun's limb. 

Besides charting the spots there are other statistics thac 
can be gathered concerning them, such as number, speed of 
rotation, and duration. From your chart you can, of course, 
get position and grouping. The size, too, is easy to determine. 
Let the diameter of the sun's image, 4 inches, for example, 
represent the diameter of the real sun 864,000 miles. If the 
spot's image is Ke inch in diameter (that is, one sixty-fourth 



76 Handbook of the Heavens 

of the sun's image), it will be one sixty-fourth of the sun's 
actual diameter or 13,500 miles. This is an average spot! 

Even if you do not have a telescope, you can make observa- 
tions of the sun, noting the rising and setting points on the 
horizon and the time of sunrise and sunset over a period of 
several months. They are dependent both upon the time 
of year and upon the latitude of the place and they follow 
definite laws. They affect the "insolation, " or amount of sun's 
rays received and are seasonal variations. 

As seen from northern latitudes, at the time of the winter 
solstice the setting sun is as far south on the horizon as it can 
get. Day by day it gradually moves northward on the horizon 
until the time of the summer solstice in June. If you were at 
the equator, you would find that on December 21 the sun 
would rise at 6 A.M. about 23^ south of the east point on the 
horizon and set at 6 P.M. 23^ south of the west point. In 
our latitudes, 40 north, it rises about 7:30 A.M. 32 south of 
the east point, on December 21, and sets about 4 130, 32 south 
of the west point. But at Oslo, Norway, the sun rises about 
2:45 A.M. on June 21, at a point 54 north of the east point 
on the horizon, and does not set until 9:15 P.M. Places with 
such high latitudes therefore have much more sunlight during 
the summer months. Above the Arctic Circle, from May until 
July, it is light almost all the time, but from November to 
January it is dark nearly all the time. Indeed, all latitudes on 
the earth's surface have definite times and places for the rising 
and setting of the sun. 

Solar eclipses, although rare for any one section of the 
earth's surface, have completely captured the layman's fancy 
and he will travel miles to see one. During the total eclipse 
of August, 1932, New England was crowded with tourists from 
all over the United States indeed from all over the world. 

Those travelers who were not " clouded out" felt well 
rewarded for their efforts. If you have ever seen the moon 
slowly creep across the face of the sun, steadily covering more 
and more of it until at last the brilliant sphere disappears and 
the corona suddenly flashes into view, you will understand why. 



Solar Observations 



77 




Yerkes Observatory 



SUN'S DISK WITH SPOTS. A 
photograph of a portion of the solar sur- . 
face, showing great groups of sunspots. 
The dark umbra of each is visible, and 
the surrounding penumbra as well as 
the lighter faculae near the edge. 




James Clark, AMNH 

SOLAR ECLIPSE. A beautiful 
photograph of the sun's corona, taken 
during the solar eclipse of August 31, 
1932. The equatorial streamers reach a 
quarter million miles from the solar sur- 
face. (From a motion picture.) 



But the corona, beautiful as it is, is not the only phe- 
nomenon visible. The prominences, huge masses of flaming 
gas thrown out to heights of thousands and hundreds of 
thousands of miles by eruptions inside the sun, are well worth 
observing. 

The Baily's beads and the "diamond-ring" effect, two 
other impressive displays seen during a total eclipse, are not, 
like the corona and prominences, actual parts of the sun which 
the eclipse makes visible. They are merely lighting effects. 
Just before the moon, moving across the face of the sun, 
shuts off the last tiny crescent of light, a few rays shine 
through the valleys along the edge of the moon. The result is 
one or several lighted dots along the dark rim of the satellite 
the Baily's beads. 

Then, just as the beads vanish, the sun's lower atmosphere, 
the inner corona, comes into view shining brilliantly. At 
nearly the same instant the pearly outer corona flashes forth. 
Along the black rim of the moon the reddish prominences lace 
into the inner corona. But almost as soon as it can be seen, the 
glorious spectacle has begun to fade. 



78 Handbook of the Heavens 

Just before the sun reappears, its outer corona is blotted 
out, but the inner corona remains for half a minute as a yellow 
ring around the sun. When the first speck of-the sun returns 
to view, irradiation makes it seem much larger than it really 
is, and the total effect is the formation of a diamond ring with 
the speck of the sun as the diamond and the inner corona as 
the ring. 

The eclipse also has its visible effects on the earth. During 
the whole time that the moon is creeping toward its central 
position and away from it, the light shining through the small 
spaces between tree leaves and through small holes, instead 
of forming the usual disks on the ground, makes tiny crescents 
images of the disappearing sun. 

Then, about ten minutes before totality, an eerie darkness 
begins to be felt. Chickens and other animals become alarmed 
and the air gets noticeably colder. Shortly before the shadow 
reaches the observer, rippling shadow bands appear on all 
light surfaces, and (from the high vantage point of an airplane 
or even a high hill) the moon's shadow itself can be seen 
advancing. Finally the moon covers the sun completely, the 
corona streams out, and the brighter stars and planets are 
visible. 

During a partial eclipse, when the moon is seen moving 
across the face of the sun although it does not cover it entirely, 
there are comparatively few observations that an amateur 
can make. He can time "first contact," when the moon 
first nicks the edge of the sun, and he can time the last contact 
(there are only two in a partial eclipse), when the moon 
finally moves off the face of the sun. At intervals during the 
eclipse he can estimate the percentage of the surface covered 
and measure the drop in temperature. 

He can also make note of the crescents cast upon light 
surfaces when the sunlight shines through leaves or small 
holes. But there is little else that can be attempted during 
a partial eclipse. 

The total eclipse, of course, provides a better opportunity 
for the observer. He can record all the phenomena mentioned 



Solar Observations 79 

above the corona, prominences, Baily's beads, diamond 
ring, temperature drop, effect on animals, shadow bands, etc. 
He can time four contacts: first, when the moon first touches 
the sun; second, the instant of beginning of totality; third, the 
instant at which totality ends; fourth, the moment when th,e 
moon moves off the face of the sun. He can count and identify 
the stars that appear during totality. 

If he is equipped with a direct-vision spectroscope, he may 
watch for the reversal of the spectrum lines from dark to 
light and light to dark as the flash spectrum of the " reversing" 
layer becomes visible just before and after totality. 

In observing the corona, prominences, and similar phe- 
nomena, note their shape and position. In the case of Rally's 
beads, count the number seen; with the shadow bands, 
measure their width and the speed and direction in which 
they move. 



Nebulae and Clusters 

IT is easy to observe bright blue, yellow, and white stars 
and even the constellations themselves, but nebulae and 
clusters are quite a different matter. They require a knowl- 
edge of star groups, the possession of a field glass or telescope, 
and perseverance. 

At first, of course, it will be rather hard to find most of the 
nebulae and clusters because they are usually hazy, dim 
patches of light. Their appearance, which distinguishes them 
from the stars, makes them difficult to locate in a telescope. 
But the search becomes easier as time goes on, soon turning 
into a treasure hunt with a long-sought nebula or cluster as the 
goal. 

Perhaps the most famous nebula is that in Orion. It is a 
huge mass of gas in a state of violent agitation, but in a 2- 
or 3-inch telescope one sees a small, peaceful greenish-white 
patch of lace. This nebula, in the middle of Orion, is the easiest 
to locate of them all. It may even be seen with the naked eye 
as the central star Theta of the easily distinguished sword. 

Sharing honors with this colossus is the great spiral nebula 
in Andromeda, the only nebula of its kind visible to the naked 
eye. In a field glass or even in a 3-inch telescope it looks like 
a thin patch of white haze a wisp of clouds but in reality 
is a tremendous galaxy, so big that light (which travels at 
the rate of 186,000 miles per second) requires 100,000 years 
to cross it. 

The beautiful ring nebula in Lyra cannot be seen with the 
naked eye but is quite easy to find in a telescope because of 
the two bright stars Beta and Gamma between which it lies. 
In a small telescope it appears as a faint, misty, round patch. 
A 5-inch telescope reveals its annular quality, and it then 

looks like a smoke ring. It is a fine planetary nebula with a 

80 



Nebulae and Clusters 81 




Yerkes Observatory Mt. Wilson Observatory 

ORION NEBULA. The only one of RING NEBULA IN LYRA. A 

the diffuse nebulae visible to the naked fifteenth-magnitude star at its center 

eye, this great nebulous mass is found lights the Ring Nebula in Lyra, 

in the sword of Orion. Messier 57. 

fifteenth-magnitude star in the center which becomes visible 
only in a huge instrument. 

A planetary nebula consists of a single star surrounded 
by a hollow sphere of gaseous material. These are com- 
paratively near the earth since they are all within our own 
" island universe," the Milky Way Galaxy. On the other 
hand, spiral nebulae like that in Andromeda are in themselves 
island universes made up of thousands of stars and huge 
aggregations of gases and cosmic dust. The Andromeda Nebula 
is the nearest of these huge galaxies, at a distance of 900,000 
light years from the solar system. The great Orion Nebula 
represents a third type, for it is a great cloud of dust reflecting 
the light of near-by stars which are associated with it. This 
class of nebula is also found within the confines of the Milky 
Way Galaxy, 

A 3-inch telescope discloses many more of these objects, 
but to see them at their best the stargazer should use a large 
home-made reflector of preferably 10- to 1 2-inch diameter. The 
larger the aperture of the glass, the more clusters and nebulae 
are within reach. Any good atlas will indicate the nebulae, 
many examples of which lie within almost every constellation 
boundary. Herschel found hundreds between Leo and Virgo, 
and the amateur is limited only by the power of his instrument. 

Although the telescope does aid the eye by gathering the 
light from a nebula and focusing it at a point, it cannot 



82 Handbook of the Heavens 




Mt. Wilson Observatory Mt. Wilson Observatory 

GREAT NEBULA IN ANDROM- DARK NEBULA IN ORION. The 

EDA. This nearest of the spiral Horsehead, a gigantic cloud of nebulous 

nebulae is an island universe similar to matter obscuring the light of the stars 

the Milky Way Galaxy. behind. 

gather enough light at any one instant to make much of the 
nebulous matter visible to the eye. A photographic plate, on 
the other hand, can collect the light until enough has been 
gathered to make a noticeable impression on the plate where 
none was made on the eye; thus the camera can "see" more of 
the nebula. A photograph of the nebulous matter around 
the Pleiades (which combine a cluster with nebulous matter) 
illustrates this fact, for such a picture shows matter that 
the eye could never see even with the largest telescope. 

Sagittarius, which contains so many objects of note because 
of its situation in the Milky Way, presents the nebula M 17, 
known as the Horseshoe Nebula, and also the famous Trifid, 
M 20. In Aquarius is another planetary nebula, M 2, a fine 
sight in a 3-inch telescope; and Vulpecula contributes the 
famous Dumbbell Nebula, which forms a rectangle with 
Epsilon, Gamma, and Beta Cygni. 

There is yet another type of nebula which is interesting 
mainly because it cannot be seen! This sounds queer at first, 
but the explanation is simple. These nebulae are the dark 
nebulae, patches of nebulous matter which are not illuminated 



Nebulae and Clusters 83 




Mt. Wilson Observatory 

MILKY WAY. A beautiful mosaic of the Milky Way the view obtained when we look 
along the plane of our Galactic System. 



by near-by stars, and which, in fact, blot out the light of 
the stars behind them, giving the appearance of a black hole 
in the sky. Indeed they were once thought to be just that, 
but the theory has been definitely disproved. There are 
several dark nebulae in the Milky Way, Orion, Taurus, and 
Ophiuchus. Those in the last constellation appear as dark 
lanes running through the group and show up nicely in a 
photograph taken with a low-power telescope. The most 
famous dark nebula of all is the Coalsack Nebula in the Sou them 
Cross a large, round, black patch. 

There is one nebula a spiral one which, although it is 
by no means the largest of its kind, can be seen on every 
clear night. It is the Milky Way, which forms the backbone 
of the Milky Way Galactic System. 

The Milky Way Galaxy is a huge, watch-shaped aggrega- 
tion of stars, star clusters, and planetary and diffuse nebulae. 
The sun is one of these stars, as are all the stars we see in the 
sky. When we see the faint band of light called the Milky Way, 
we are, in reality, looking out into space along the plane of the 
Galaxy, where the stars are thickest. 

The Milky Way is always in some part of the sky. It never 
sets entirely below the horizon, but sometimes it is so faint 
that it cannot be seen. The glare of near-by street lights is 



84 Handbook of the Heavens 




Mi. Wilson Observatory Yerkes Observatory 

MESSIER 13. The Great Globular DOUBLE CLUSTER IN PER- 

Cluster in Hercules, a group of over SEUS. This twin cluster (Chi-h), con- 

50,000 giant suns, known in star cata- taining thousands of stars in two open 

logues simply as M 13. clusters, is a brilliant telescopic object. 

often sufficient to blot it out, and a slight haze or mist in the 
sky is fatal to the hopes of those who would see it. 

Running directly overhead during the winter evenings, the 
great arc of light begins to drop toward the western horizon 
in March. Early in May, at about 8 o'clock in the evening, it 
is almost resting on the edge of the sky; it stretches along the 
horizon from a point almost due southwest, northward around 
the compass, to the point that is due east. At this time it 
provides a filmy lace border to five-eighths of the sky, but 
it is barely visible because of the thicker layers of atmosphere 
at the horizon through which the light must pass. 

Three hours later part of the Milky Way will have set. 
But the Milky Way is a great circle of light that extends around 
the entire sky, and another arc of it has already risen in the 
east. This continues to climb and late in July, at 8 P.M., it is 
halfway toward the zenith. By the same time in September 
or even at 5 P.M. the following morning it is overhead again, 
and it remains so during the evening for the rest of the year. 

No one is prepared to say how many stars there are in the 
Milky Way Galaxy. Every naked-eye star in the heavens 



Nebulae and Clusters 85 



TAURUS 



'.V- 



: V i V * ' .' Pl i*des ^ *- ... 6 . 

*,,;.**""" *""" ; 



M35*, 



GEMINI 
6 

,7,*"^ * ^" " 

1549 i 



belongs to it, and the river of light that earned it its name 
contains millions of dim stars. Modern estimates place the 
number of suns in this Galaxy at more than a hundred thou- 
sand million. 

The diameter of this Galaxy is probably about twice that 
of the Andromeda Nebula. It rotates constantly about the 
center of the system, which is believed to lie near the constella- 
tion of Sagittarius. The sun, located about one-half of the way 
out from the center of the galaxy, requires something more 
than 200 million years to perform a complete revolution, 
although it is traveling around the axis of the system at about 
200 miles a second. 

Few nebulae are visible with low power as compared with 
the huge number of clusters or groups of stars that can be 
seen and studied with little optical aid. Some are very small, 
consisting of less than a hundred stars, while others range up 
into the thousands. Of course, with a field glass or 3-inch 
telescope, one can view only the larger ones. 

The best known of these vast swarms of stars are the 
Pleiades and the Hyades, both in the constellation of Taurus, 
the Bull. They are examples of loose clusters in which the 
stars are moving in the same direction at approximately the 
same speed. Even with low power they are a wonderful sight, 
and as the magnification increases the number of stars that 
can be seen also increases. We may never be able to plumb 
the greatest depths of these vast swarms. 

The Hyades to the naked eye look like a V of faint stars, 
with the first-magnitude star Aldebaran in their midst. Here 



86 Handbook of the Heavens 



MONOCEROS /~-->. 

-'"' / *'1424 

2 ^ M220 

v* 9 *"' * -"^ 



' f 

1637 






SAGITTARIUS 

S 



is a good region to test eyes, field glass, and telescope and 
to see how many objects may be counted with each. 

The Pleiades are a loose cluster of stars; six stars (seven 
with very good eyesight) can be seen with the naked eye, 
arranged in the form of a dipper. In exceptionally clear skies, 
such as those of Arizona and New Mexico, as many as eighteen 
have been seen with the naked eye. Great magnification reveals 
countless stars in the region, and long-time exposure shows 
nebulosity enveloping the major stars in the group. 

Praesepe, the cluster in Cancer, contains 85 stars down to 
tenth magnitude and 358 down to eighteenth. Beyond that 
they have not been counted but there are probably many 
hundreds more. An interesting thing about this Bee Hive 
cluster is the fact that it is so faint that the slightest wisp 
of cloud will obscure the cluster. 

In Perseus is the double cluster Chi-h set in a rich region of 
the sky "sown with scintillating stars." On exceptionally 
clear nights the pair are faintly visible to the naked eye. In a 
field glass they appear to be two interesting patches of in- 
numerable stars; the number seen is a good test of the aper- 
ture of the glass and "seeing" conditions of the atmosphere. 

The region enclosed by Auriga's pentagon has several 
clusters. Two are visible with a field glass, while a 3-inch 
telescope discloses seven. M 37 and M 38 are especially 
interesting. Of course, one must not expect to see separate 
pin points of light, for only patches of haze will greet the 
eye and it is necessary to have a large telescope to resolve 
the haze into separate stars (for their location, see page 91). 



Nebulae and Clusters 87 

Gemini offers M 35, one of the most beautiful clusters in 
the sky. In a 3-inch telescope it is exquisite, for the red star 
in its center is visible. It is very near Eta, and, close by, 
Uranus was first sighted by Herschel. Just beside Delta is 
1549 another challenge for the cluster hunter and near by, 
in the head of Monoceros, is 1424, while near the tail of the 
same group is 1637. 

Last but not least is the cluster M 8 in Sagittarius, which 
is in the midst of a rich and gorgeous field where many interest- 
ing objects can be found with a 2- or 3-inch telescope. On an 
exceptionally clear night one cluster, M 22, can be seen with 
the naked eye about 3 northeast of Lambda (X). M 24 and 
M 25 should be found as well as M 17 and the Trifid Nebula 

M 20. 

There are many other clusters which can be easily seen 
with a 3-inch telescope but which are not unusual enough to 
be separately named and discussed. A good atlas will show 
clusters in almost every constellation. Portions of the sky 
which contain a great number of these make up very fine 
star fields. The region east of Leo, for instance, contains 
many hundreds of small clusters which appear as hazy specks 
of light when viewed with a 3-inch telescope. 



Variable Stars 

THE observation of variable stars is a field of astronomical 
research that is left almost entirely to the amateur and he 
can handle the assignment quite well, because no complicated 
or expensive instruments are needed in order to work with 
the brightest stars. A small telescope a 3-inch refractor, 
for instance makes a good instrument, and it is sometimes 
possible even to use the naked eye. However, there are vari- 
ables of all magnitudes, and some of them need a 5- or 8- or 
ID-inch instrument. 

A fact that adds to the interest of variable-star observing 
is that 'the cause of the light fluctuations of many variables 
is still a mystery, and only through hundreds of very accurate 
observations can a solution be reached. 

A variable star is one whose magnitude changes from 
time to time, these changes in some instances being slight 
but in others very great. Variables are generally classified 
as "short period" when the cycle is completed in a few days 
or so and "long period" when the cycles are much longer 
in some cases even years. 

Short-period variables may be subdivided into two classes. 
In one, variations are caused by a partial eclipse of the brighter 
star by a companion star of lesser brightness (see diagram on 
page 71). Algol, in Perseus, is a good example of this type. 
For the other subdivision, the variations are caused by some 
change in the stars themselves. They alternately blaze up and 
die down for some reason which is still a mystery. The variables 
of this class are known as Cepheids because the first of the type 
was discovered in Cepheus. These Cepheids were the first 
stars used to help measure Galactic distances. 

The cause for variation in the long-period variables is not 
known, but one theory states that spots, corresponding to 

88 



Variable Stars 89 

our sunspots, may have cycles of more or less than II years 
and may cover a larger area of the star. 

Some stars of this class, such as R Coronae, are ordinarily 
bright and then darken for a few weeks; others are dark most 
of the time but then occasionally rise in brilliance; still others 
rise to unheard-of brightness and then fade and remain out 
of naked-eye vision for years. This type has been found only 
in the southern hemisphere. 

On the whole, long-period variables are irregular and range 
from two or three months to two or three years in period. They 
seen to "scorn" constancy, and the maximum of one rise may 
fall far short of the previous brilliancy. The change of bright- 
ness in these stars is often great; the range from minimum to 
maximum is sometimes over a hundred, even a thousand, 
times. They are giant red stars, with low density and great 
luminosity many times the brightness of our sun. 

Novae, new stars, which flare up where no star was visible 
before and then gradually fade away, are usually classed as 
variables. In late 1934 a new star appeared in Hercules. Nova 
Herculis, as it was known, rose from twelfth magnitude to 
first, and then quickly faded from naked-eye view. A com- 
pletely satisfactory explanation of this type of star is still 
lacking. 

The best known of the long-period variables probably is 
Mira, or Omicron Ceti. It has a wide range, from magnitude 
1.7 to 9.5, and goes from maximum to minimum in about 
331 days. Slight irregularities in its variation increase the 
interest of this star for the amateur, and it can be observed 
throughout its entire period with a 3-inch glass. This great 
giant has a diameter of perhaps 260 million miles and could, 
therefore, contain the whole orbit of the earth, and much 
more, within its vast bulk. 

For those amateur astronomers who do not have telescopes 
there are many variables that can be observed through their 
whole cycle with the unaided eye. Algol, Beta Persei, is the 
most interesting of these. Its short period, 2 d 20 h 48, is known 



90 Handbook of the Heavens 

with great accuracy. It is an eclipsing binary, ranging from 
magnitude 2.3 to 3.5. 

The star Rho Persei is another variable whose period is 
very irregular. It should prove interesting to compile a list 
of observations of this star which undergoes a change of about 
a magnitude in five or six weeks. 

Before entering the subject of how to observe variable 
stars, it is interesting to note that our own sun is a long- 
period variable. In this case the chief variation is brought 
about by the eleven-year sunspot cycle. 

In observing and recording the actual amount of a star's 
variation, bear in mind these facts: first, the human eye 
without long training cannot estimate accurately divisions 
smaller than one-third of a magnitude; and, second, the method 
to be used depends entirely upon the star in question. 

The first method employs comparison with stars in the 
vicinity of the variable. Take two which are about two 
magnitudes different in brightness, rather near each other, 
and which encompass the entire range of variability. Try to 
estimate the brilliancy of the variable as accurately as you 
can. If these stars are less than two magnitudes apart, do 
not attempt such fine estimation as tenths. For example, 
supposing them to be at least two apart, if the variable in 
question were, as nearly as you could tell, the same brightness 
as the fainter of the two stars, it would be recorded o.o. If 
it were halfway between, it would be recorded 0.5. If you 
have no comparison stars conveniently near, the best method 
is to estimate the brilliancy in relation to any standard star. 
The disadvantage of this method is that the sky may be hazy 
at a point where the standard star is located, thus introducing 
an error. 

The observation of telescopic variable stars is one of the 
most fascinating bits of work that a telescopist can undertake. 
Patience and perseverance are the only requirements needed 
aside from the small telescope. 

These pulsating stars are designated both by the Harvard 
designation number and by letters. The numbers consist of 



Variable Stars 





CASSIOPEIA ..^ 


AURIGA 


*^^-^iW 


J&- 


/? V a 


s * v 


. x c " 


f ' a ip c 


4^ '* 


M37 /* 


^"^f^RSEUS 


i-1-4 


P* Algol 




* 




v~* 



2.9 
2.8 
2.7 
2.6 
2.5 
2.4 
2.3 
2.2 
2.1 
2.0 ( 


Light Curve of Delta Ccphei 


M 








1 . 


^ 


















A 








\j 




y 
















6 








\l 




\ 
















N 








V 






x 














1 








I 








\ 












T 








l\ 










y 








* 


H 








1 










V 


^ 








D 


^ 






f 














\ 






E 






^ 


ID 




A 




Y 




S 




^s. 


^ 


) 1 2 3 4 5 6 7 



six digits, divided into three units: the hour and minute of 
right ascension and the degrees of declination for the year 
1900. If the last two digits are underscored or italicized, 
southern declination is indicated. Thus, 094211 would be the 
designation number of R Leonis: g h 42 right ascension and 
+ 11 declination. 

An outline of the procedure to be followed in the observa- 
tion of variables may be secured from the American Associa- 
tion of Variable Star Observers as well as star charts especially 
devised for this work. In using charts at the telescope, it must 
be remembered that the astronomical telescope shows the 
stars in an inverted field. Therefore the chart must be inverted, 
unless prepared to represent them as they appear in the field 
of view. 

If the telescope in use is not equipped with declination 
circles, it will be necessary first to plot the position of the 
variable on a star map and then to pick up the field by guiding 
from some bright star in the vicinity of the variable. 

It is useful to determine the diameter of the " field of view" 
of the telescope. To find this diameter, focus the telescope on a 
star which is as close to the celestial equator as possible and 
time its passage from one side of the telescope field to the other. 
This time interval, in minutes, divided by 4 is equal to the 
diameter of the field in degrees of arc exactly what is required. 

In actually locating the variable we wish to observe, in 
this example, R Leonis, let us suppose the diameter of the 
telescope field is i and that the telescope is focused on Omicron 
Leonis. It would be seen by examining a chart of the naked- 



92 Handbook of the Heavens 

eye stars near R Leonis that it (R Leonis) is just about ij^ 
east and I y north of Omicron. So the first movement is to 
move the telescope east just two diameters of the field. This 
brings the point that is I y east of Omicron into the center of 
view. 

From this point the telescope is moved north I J^, and now 
you should be able to recognize the field from the chart and 
pick out the variable. Two bright stars, pointing southeast, 
with a little equilateral triangle south of them would be seen. 
The variable star is one of the members of the little triangle 
and by proper orientation of the chart you should be able to 
identify it quite easily. Of course, all variable fields are not so 
easily found, but by clear thinking and patient work they may 
. be located if within range of the telescope in use. 

Now that we have tracked down the variable, our next 
task, of course, is to estimate its magnitude. Other stars in 
the field' whose magnitudes are known are used for estimating, 
as has been explained. Suppose, for example, the brightness 
seems to be just about between 9.0 and 9.6 (using the other 
two stars in the little triangle for comparison). R Leonis is 
then recorded to be 9.3 magnitude at that particular date and 
time. This method is only a slight departure from the procedure 
previously outlined, but it serves to show how circumstances 
may alter that procedure somewhat. No absolutely definite 
rule can be laid down in this work because all working condi- 
tions cannot be foreseen. The method given, however, can 
with little adaptation be used in almost every case. 

To aid the observer to get more accurate results it may 
prove expedient to push the eyepiece just a little out df focus, 
getting little lighted disks instead of mere pin points of light. 
Disks of light are much easier to compare for brightness than 
points of light. 

The method of recording variables is simple; merely con- 
struct a graph. Along the top record the time, usually in days 
(fractions may be estimated), and along the side place the 
magnitude (see diagram). Consult a star catalogue and find 
the actual magnitudes. 



Variable Stars 



93 



Below are listed several of the many variable stars which 
furnish excellent observational material throughout the year. 



Star 


Magnitude 
range 


Period 


OL Cassiopeiae 


22-28 


Not periodic 


o Ceti 


1.7- o . c 


33 i d , irregular 


p Persei 


7.4. 4.2 


33 , very irregular 


j8 Persei 


2. i- 7. ? 


2 d 20 h 48 m 


X Tauri . 


1.8- 4 i 


1 d 22 h i?2 m 


Aurigae 


i.o 4.. c 


Not periodic 


a Orionis 


0.7 i . c 


Irregular 


R Canis Majoris 


C Q 6 7 


d h m 


77 Geminorum 


3242 


2 3 i d 


f Geminorum 


1 7 4 S 


io d 03 h 4i m 


T Vulpeculae. 


t; c 6. c 


4 d io h 27 m 


/i Cephei 


4.. o c c 


43 o d 


d Cephei 


i 6 4 7 


5 d o8 h 47 m 


/3 Pegasi 


2.2 2.7 


Irregular 


R Aquarii 


5 8 n.o 


l87 d 


R Leonis 


5.0-10.8 


3io d 


S or 10 Sagittae 


c 4. 6 I 


8 4 d 


5 Librae 


4.8- 6.2 


2.3 d 


U Herculis 


4 8- c i 


2 OC d 


(x Herculis 


I.I 1.Q 


Irregular 


8 Lvrae 


^ . J 4 I 


I2.QI d 


i) Aquilae 


1.7 4 . ? 


7.i8 d 


W Sagittarii 


4.1- ?. I 


7 . 59 d 


XCvrni 


4 211 7 


40Q d 


R Hydrae 


1. ;-io. i 


4o6 d 









The A. A. V. S. O. was formed in 1911 to relieve profes- 
sionals of the work of observing variables. This association 
has members all over the world, and some of the most active 
ones make thousands of observations in the course of a year. 
The data are published in Popular Astronomy. If one really 
becomes interested enough in observing variables and wishes 
to take up the work as a form of research, it is advised that 
he write a letter of inquiry to Leon Campbell, Recorder of the 
A. A. V. S. O., Harvard College Observatory, Cambridge, 
Massachusetts. 



Hints on Telescope Usage 

MOST of the material in this handbook is made very much 
more interesting when the observer is aided by a telescope or 
field glass, whether small or large. But even with one of these 
instruments to help him, he may miss a great deal of impor- 
tance through lack of knowledge of how to use it. 

When the purchase of a telescope is considered, it is well 
to remember that refracting telescopes are superior to reflectors 
in certain respects. They are less liable to be damaged by 
inexperienced handling or from neglect, and they offer a wider 
field with good definition. Reflectors are much cheaper, when 
taken aperture for aperture. But it is necessary to resilver 
reflector mirrors every few weeks and this is troublesome, 
expensive and requires much skill. So while the initial cost may 
be greater for a refractor, it obviates this perpetual annoyance 
of reconditioning (including frequent centering of prism, 
mirror, etc.). However, a new aluminizing process which makes 
the mirror surface both permanent and washable is now within 
the amateur's budget. 

In selecting a telescope it is preferable to get a smaller 
aperture and good lens, with a good mounting, than to get a 
large telescope with an unsteady mount or poor lens. 

The highest magnification that a good telescope can stand 
depends upon (i) quality of objective, (2) quality of eyepiece, 
(3) condition of mounting, (4) state of atmosphere. Moreover, 
the highest magnification is seldom used, each celestial object 
and condition of atmosphere determining the proper power to 
use at the moment. The magnifying power of a telescope is 
determined by the focal length of the object glass divided by 
focal length of ocular used at the time. (Larger lenses admit 
more light and make the image brighter.) But if one were to 
take two telescopes, one with an objective I inch in diameter 
and the other with an objective 40 inches in 'diameter, one 

94 



Hints on Telescope Usage 



95 



Refracting Telescope with 
itf! Mounting 



Slow motion in 
declination \ 



Finder 
Eyepiece 



Objective 
Declination 



Declination 
circle 

Counterweight 



Screen for 

observing 

sun 




Slow motion 
'in hour angle 



mage 



would find that they had the same magnifying power, pro- 
vided their focal lengths were the same. However, there 
would be a great difference in the images. 

Telescopes themselves, no matter how fine the lenses, are 
made less efficient through lack of good mountings. In fact 
the mounting is an integral part of the telescope. And the 
first requisite of a good mounting is firmness. There must 
be no looseness at the connection between tripod and instru- 
ment which will result in " dancing stars." 

The simplest mounting is the type known as the altaz- 
imuth found almost universally in small telescopes. Although 
it is efficient up to a certain point it is not easily adapted to 
certain types of work. The altazimuth mount may consist, 
in one form, of nothing more than a universal joint which 
permits movement in any direction, horizontally, vertically, 
or diagonally. Variations are numerous, but, broadly speaking, 
this mounting is one which allows free motion of the telescope 
in any direction. 



96 Handbook of the Heavens 

The greatest weakness of the altazimuth mounting lies in 
the fact that when the earth rotates, carrying the instrument 
with it, the star moves out of the field of view and the tele- 
scope must be moved in two directions, or their resultant, to 
find it again. This inconvenience and waste of motion are also 
met with when first locating an object. 

All observatories and many amateurs have their instru- 
ments mounted on an equatorial. With this mounting they 
overcome the inconvenience of the altazimuth and derive 
several additional advantages. But equatorials are more 
difficult to construct and much more costly to buy. Briefly, 
the equatorial mounting consists of a polar axis and a declina- 
tion axis at right angles to each other, as shown in the diagram 
on page 95. The polar axis is adjusted to the latitude of the 
observer so as to point toward the celestial pole, and as a 
result it is parallel to the earth's axis. The circle in the dia- 
gram' graduated in hours and minutes of hour angle, and 
known as the hour circle, is attached to the polar axis. As 
may readily be seen, it will be parallel to the earth's equator. 

The polar axis is set quite firmly on the tripod or pier which 
supports the mount. Fixed to one end of it at a right angle is 
the declination axis, and at the other are a graduated declina- 
tion circle and a counterweight. The declination circle and the 
counterweight also appear in the diagram. 

Having once pointed a telescope so mounted at a star, 
only one motion is necessary to follow it, that is, motion in 
hour angle. The declination axis is not touched, only the polar 
axis is moved, and this in a direction opposite to that of the 
earth's rotation. Since the polar axis is parallel to that of the 
earth, its movement counteracts that of the earth, and 
the star under observation remains constantly in the field of 
view. 

Equatorial telescopes have accessories, and one of the 
most important is the driving clock. This clockwork mechanism 
turns the polar axis at a steady rate of speed, relieving the 
observer of this work. But relatively few private telescopes 
are so equipped and most of them are guided by hand. The 



Hints on Telescope Usage 97 

equatorial also eases the task of " picking up" an object in- 
visible to the naked eye. Having obtained, from the Nautical 
Almanac, an atlas, or ephemeris, the right ascension and 
declination of an object (see the "Observational Scrapbook," 
page 115), one needs also to know the sidereal time. The 
sidereal clock which is rated to gain I second in every 6 min- 
utes of ordinary time is an invaluable accessory for this work. 
If one does not have a real sidereal clock or watch, he may use 
an ordinary timepiece, computing sidereal time from solar 
time by using the Nautical Almanac. When right ascension 
and declination and sidereal time are known, the circles of 
the equatorial mounting may be set so that the telescope will 
point directly at the as-yet-unseen object. 

With the aid of an equatorial mounting which follows 
the stars steadily, it is possible to make fine pictures of star 
fields, planets, etc. Details will be found in the chapter on 
"Amateur Astronomical Photography" (page 109). 

A zenith prism is an almost essential piece of equipment 
for observing objects nearly overhead. It makes for far greater 
comfort by throwing the image off at right angles to the 
telescope so that the observer does not have to maneuver his 
head into a position directly at the end of the tube. But while 
the image, when seen through an astronomical refractor with 
an ordinary eyepiece, is inverted or turned upside down, it 
suffers a worse fate when observed through a zenith prism. It 
is then reversed in such a way that certain objects, say the 
moon, cannot be checked easily, for the observer cannot 
turn the moon chart in any position to coincide with the 
telescopic view unless he looks through the back of the paper. 
Whereas, when looking straight through a refractor, he turns 
the chart upside down, if indeed it may not already be pub- 
lished so, with north at the bottom, etc. However, ordinary 
field glasses and terrestrial telescopes do not have inverted 
but erected images. 

Should you desire to determine the colors of a double, put 
the image out of focus so that the stars appear as blurred disks. 
The color will be more readily apparent, at least according to 



98 Handbook of the Heavens 

some observers, as the eye is more sensitive to the color of a 
disk than to that of a point of light. But an important point 
here is the quality of the telescope's objective, for it should 
be free as much as possible from chromatic aberration which 
causes colors to form around a brilliant object. The "apo- 
chromat" lens is superior to all others in this respect. And, of 
course, for all colored objects the refracting telescope cannot 
rival the reflector. No color estimate can accurately be made, 
if the object under observation is within 10 of the horizon, 
because absorption, among other things, causes it to change 
color rapidly. 

When attempting to find Neptune, an asteroid, or other 
telescopic objects, the first task ahead is really not telescopic 
at all. If you have not a chart showing the object's position 
for the night on which you are observing, you must make one. 
This is no small task, as you must use charts with stars below 
the magnitude of the object observed and go through computa- 
tions to allow for precession, also interpolations so as to do the 
plotting. Include in the map all the stars near the object under 
observation, so as to make identification of the field easier. 

The Handbook of the Heavens eliminates much of this 
work by including maps of the planetary positions. In the 
actual observing of the object, first locate the nearest naked- 
eye star, and then work from that in the telescopic field, 
identifying the fainter stars on the charts, until the object of 
the search has been found. If any question as to its identity 
remains, if it is an asteroid, comet, or planet, keep watching 
it until it has undoubtedly changed its position with relation 
to the other stars on the chart. It will do so in a night or more 
if the search has been successful. 

As a general rule, it will be found more convenient to 
use low-power magnification on these objects particularly 
because it gives a wider field. The high powers will cause the 
object to pass rapidly out of the field and will exaggerate 
imperfections of the object glass and " jiggling" of the mount- 
ing, if it is not a very good one. They will also exaggerate 
the atmospheric irregularities, such as rising heat waves, dust, 



Hints on Telescope Usage 99 

differences in temperature within and without the telescope 
tube, and will always magnify tremors due to wind. 

When using a flashlight in observation work, cover it or 
mask it with red tissue paper or cloth, so that the glare does 
not affect the eye. Should the mounting be unsteady in itself 
(not because of the wind), point the telescope ahead of the 
object under observation. Then, by the time it moves into 
the field, the movements in the mounting will have had a 
chance to settle down. 

When cleaning lenses, always use the softest tissue obtain- 
able and rub gently. Have a dew cap constantly over the objec- 
tive when it is not in use. A person who is not experienced 
in handling telescopes would best let alone the silver of a 
mirror or the cell of an object glass. 

Telescopes of 3 -inches or greater aperture should be 
equipped with a small finder, which is a little telescope attached 
to the tube of the large one and mounted parallel to it. It 
saves much time when locating star fields in which any object 
is to be found. It would take some ingenuity to make one of 
these at home, although it has often been done. Try to get an 
achromatic 2-inch lens objective, 8 to 10 inches in focus, and 
a i -inch ocular (Huygens type) and make a miniature telescope 
or the instrument may be purchased complete. 

In observing comets, star clusters, nebulae, and other 
faint objects, it is best to look somewhat away from the 
object if the latter be very faint. Objects viewed in this 
manner appear brighter than when seen by looking squarely 
at them. This is known as averted vision; by looking as 
suggested one frequently finds many small stars that were 
invisible when observed straight on. 

When observing double stars, use, if possible, the approxi- 
mate magnification suggested for them in the chapter on 
"Double Stars" (page 69). After you have graduated from 
the outstanding examples presented in this handbook, you 
will have had enough experience to judge for yourself the 
magnification. A general rule for finding the resolving power 
of your telescope would be to divide 4^56 by the diameter 



ioo Handbook of the Heavens 

of its objective or mirror in inches. Thus a 2-inch telescope 
cannot resolve doubles closer than 2^28; therefore, all doubles 
are notoriously easier to separate when a large glass is used in 
preference to a small one, because the aperture increases 
resolution. 

A "moon glass," to use the Zeiss term, a neutral glass 
tinted very slightly, will make observations of the moon less 
tiring to the eyes especially when using a telescope of large 
aperture. A "sun glass" is a transparent heavily tinted glass 
for the ocular. 

Really to enjoy stargazing beyond the beginner's stage, 
one will want a good star atlas. Norton's, Schurig's, and 
Stuker's are suggested. 



Asteroid Hunting 



IN THE vast gulf of space between the orbits of Mars and 
Jupiter lies the asteroid zone. In this broad zone, circling 
perpetually around the sun in giant ellipses, may be found 
between one and two thousand diminutive worlds. These are 
called not only the asteroids but the minor planets; in fact 
their name, literally translated into English from several 
other languages, means " little planets." For they are just 
as much planets as are Mercury and Mars, only smaller and 
of less importance. 

The following table gives data concerning the first four 
asteroids discovered, and consequently those best known and 
easiest to observe. 



Asteroid 


Discovery 


Diameter, 
miles 


Albedo 


Average magnitude 
at opposition 


I Ceres 


Piazzi, 1801 


480 


.06 


7 M 4 


2. Pallas 


Olbers, 1802 


-3 O4. 


. 07 


8.0 


3. Tuno 


Harding, 1804 


I 2O 


. 12 


8.7 


4. Vesta 


Olbers, 1807 


24O 


.26 


6.5 













From this table it is seen that they are all very small 
bodies, astronomically. Many hundreds are smaller than 
these, with but a few miles of diameter, and some are suspected 
of being not over a mile in diameter. 

The asteroids are probably barren worlds without water, 
atmospheres, or living things, and with temperatures far below 
freezing. Many have rocky or mountainous surfaces as shown 
by their disproportionate change in brightness with a change 
of phase. 

There are over 1,300 minor planets that are so well known 
from observations that the elements of their orbits are known 
and published and ephemerides calculated every year. This 



101 



IO2 Handbook of the Heavens 

laborious work in celestial mechanics is undertaken by the 
Astronomisches Rechen-Institut, the world's headquarters for 
asteroids, in Berlin-Dahlem, Germany. Each ephemeris gives 
the exact right ascension and declination of an asteroid for 
about 6 weeks around opposition time, when it can be observed 
best. 

Most of the asteroids are of fainter magnitude than the 
first four in the foregoing table. Brightness varies with the dis- 
tance of the object from the earth and the phase of the 
illumination; but there are other variations, and it is likely 
that they are caused by the combination of rotation of the 
spheroid, with difference in the reflecting power of different 
portions of the surface. The brightness of Eros in 1931 was 
found to have a periodic variation of a few hours, and it is 
thought that this is to be correlated with its rotation period. 
The average magnitudes of all the known planetoids go down 
to 1 8, and the aphelion magnitudes of some are as faint as 20. 
These can be observed only in the greatest telescopes, if at all; 
actually observations are made by the photographic plate 
exposed a long time. The largest number of asteroids seem to 
have an average opposition magnitude of 13; there are 404 
of them; next comes fourteenth magnitude, with 360 planets. 
It can readily be appreciated that only a few are within range 
of a small telescope, and usually one or two are available for 
observation in a 3-inch instrument. 

Asteroid hunting is of two kinds professional searching 
with the astrocamera and observation with a small telescope. 
Professional asteroid work is done in a large observatory 
specializing in this field. There the method consists of exposing 
a plate in an " astrographic camera" for sometimes as much as 
two or three hours. When the plate is held, by guiding, on 
the stars, the asteroids leave short trails. But if the plate is 
moved during exposure to correspond with the motion (with 
respect to the stellar background) of an average asteroid for 
the particular region, then the planet appears as a small point. 
Its image is denser on the negative, from accumulation of 
light, than it would be as a trail. Very often plates contain 



Asteroid Hunting 103 

images of several planets. These are then "reduced/ 5 or the 
planets' positions determined in the laboratory, and a com- 
parison is made with places of known asteroids. After several 
observations of one object are made, preferably at intervals 
of some weeks, the computers are able, as in the case of new 
comets, to determine the orbit and construct an ephemeris. 
Such an ephemeris is really a prediction of the exact positions 
of the asteroid in the sky at stated times. 

The second type of observation depends on these ephem- 
erides, for it consists in locating the planet in the telescope 
from the ephemeris positions. Such is the kind of work out- 
lined in this handbook. 

If you are observing, you are commonly using the telescope 
on dates lying between the ones marked on the charts supplied 
with the handbook, so that you must obviously mark the 
position where the asteroid should be at the moment of 
observation. Then you are ready for observing. 

Carry the telescope into a really dark place, open to the 
constellation containing the asteroid. If it is an astronomical 
telescope, it inverts the image. If, therefore, you are looking 
toward the meridian, anywhere near the equatorial regions 
of the sky, south is at the top, north at the bottom, west on 
the left, and east on the right in the field of view. As you move 
the telescope to the west, all these points of direction rotate 
clockwise; or if you move to the east, they rotate counter- 
clockwise. Hold the chart near the telescope (using a dim light) 
and tilt it so that the north-south line in the chart is parallel 
to the hour circle of the field of view and inverted that is, 
with the " south" of the chart toward the north celestial pole 
not the north horizon. Then after a few moments of being in 
darkness, you can see the star configurations just as they are 
in the chart. Locate first the brightest star of the region near 
the asteroid, and gradually move the field of view to the 
asteroid, identifying all the stars by their configurations 
and relative magnitudes as on the diagram. The asteroid 
should be found in its proper place, according to the date of 
observation with respect to the dates marked on the chart. 



IO4 Handbook of the Heavens 

With practice, and good sky conditions, identifications can 
often be made in a few minutes. At times they have even been 
made instantly. 

It is interesting to follow these objects from night to 
night. Except at the stationary points in their apparent 
paths, a movement from night to night can be noticed. Indeed, 
if after observing a few times an interruption of a few nights 
takes place, more time will be needed on the next observation 
to identify the new star fields in which the moving object is 
now found. With the technique as outlined above, some 
observers follow asteroids through many weeks' time. 

Half of the entire work of picking up asteroids or other 
objects invisible to the naked eye lies in the plotting of the 
course. There are other possible ways, but this is the most 
practicable method, for a month's path is done in an hour 
or so, and further work is all at the eyepiece of the telescope. 
Positions are taken from the current ephemeris of the planet 
to be located. These positions could be plotted at once on a 
good star chart, if there were no precession of the equinoxes, 
causing a constant change of reference points. But any one 
star atlas has fixed coordinates of right ascension and declina- 
tion. This framework of coordinates is placed in position on 
the atlas according to the actual positions of the vernal 
equinox and celestial pole for any specified year. Obviously 
it cannot be changed to match the equinox of every ephemeris 
published, without a new edition of the atlas every year. 
While the yearly change is very small, it is cumulative and 
throws an object out several minutes for a number of years of 
equinox change. Now, the star charts have their equinoxes 
placed to correspond with equinox positions of standard star 
catalogues. So, in plotting, one must allow for precession. 

Reduction for precession is effected by trigonometric 
formulas, tables, interpolations from precession data on the 
charts. The result is a new ephemeris to match the equinox 
of the chart. Then very careful plotting with an accurate scale 
divided into half millimeters will establish positions for certain 
dates, for o G.C.T., and through these points a smooth curve 



Asteroid Hunting 105 

must be drawn. (A star atlas that has star magnitudes fainter 
than the minor planet under consideration must be used.) 
Comet paths are made similarly. The difficulty involved varies 
with the place on the celestial sphere where the object is to be 
found. Plotting star paths is very troublesome as the region 
approaches a celestial pole and in a way is increased also if the 
object has a large motion from day to day, like most comets, 
for then an hour's work will not cover such a long period. 

Asteroids are not spectacular in the telescope. They cannot 
be distinguished by appearance from a star of the same magni- 
tude, except that possibly they sparkle less, and some of 
them, like Vesta, do have characteristic colors. However, their 
daily movement against the stellar background is a positive 
indication of their character. But a telescope user gets much 
practice and fun, too, and even a thrill from following the 
movements of these tiny worlds, which may be but 100 miles 
in diameter and 250 million miles away! 



106 Handbook of the Heavens 

Chart of fiesta 

Our large-scale chart of Vesta shows a typical retrograde loop 
performed by the planet during the latter half of 1935. The con- 
tinuous line shows the apparent path of the asteroid among the 
stars for several months, and the planet is expected to be at the 
exact positions given at 7 P.M. (Eastern Standard Time) on the 
dates specified. At intermediate times the observer must interpolate 
the position for himself, which is done before going to the telescope. 

In observing, the north-south line of the diagram is oriented to 
correspond with the actual directions in the heavens, the north 
pointing to the north celestial pole. If your instrument is a ter- 
restrial glass with an erected image, the field of view will correspond 
to the chart; if, however, you are using an astronomical telescope 
with inverted image, invert the chart and have the chart's south 
pointing to the north celestial pole. 

Locate first one of the brightest stars; for instance, if observing 
in the first half of November, center on the group d and 77 Aquarii. 
After these key stars are located in the field of view, the smaller 
stars and objects can be discerned. Usually the chart will have to 
be tilted in orientation, and the asteroid will commonly be between 
the dates marked. 

Vesta varies in brightness during the year, its maximum being 
almost sixth magnitude on September 3. In December it is about 
8 and the average for the period is about the same as the star 74 
Aquarii. It will be noted that several telescopic stars will be in 
exceedingly close conjunction with Vesta during this half year, 
as on August 16. The daily motion of this planet with respect to 
the stars (not the "diurnal motion" through the sky) can be 
observed whenever it passes close to a star, at such times the 
motion can be detected in one night's observation. 

Chart of Juno 

In Juno's course among the stars for the latter part of 1935, 
it will be seen to be moving southward until November 27, this 
direction constituting its retrograde motion. This asteroid is 
fainter than Vesta. After starting with magnitude 8 in August, 
it will become brightest in October with magnitude 7.2, which 
will fall to 7.8 in December. 

First pick up a. Piscium, a naked-eye star, and then move the 
telescope field gradually to the asteroid, identifying all the con- 
figurations. Juno is more difficult than Vesta to locate at this time, 
as fewer bright stars lie near Juno's path. 



Asteroid Charts 



in 
ro * 



' " ' 



-_ L n . T . 

: so . p . .ov ...: -% .. 



" " H . " " " . * *, 07 07 * **" 

(/); . . . c &- c 
: w ; . 2 ;. ; : f&X^ ' 




. .4W3*w 



107 



Handbook of the Heavens 



North 



JUNO :. 

' '. 935 
' *v '". 




South** 



108 



Amateur Astronomical Photography 

PICTURES of the great rambling nebulae, globular star clusters, 
comets, and similar astronomical subjects are used profusely 
to illustrate books and articles dealing with the stars, and 
undoubtedly the reader has sometimes wished that he too 
might make such photographs. 

Unfortunately, pictures of this nature require much elabo- 
rate apparatus including an expensive telescope and an 
equatorial mount driven by clockwork. They are not, of course, 
made primarily to illustrate books but to aid modern astro- 
nomical research. The astronomer lets the patient eye of the 
camera, which never tires and which sees far more than the 
human eye, do much of his laborious- observing for him. Then 
he examines the plates at his leisure. 

Although the apparatus needed for such pictures is far 
beyond the reach of the beginner, anyone who is the owner 
of a good camera and has a little knowledge of photography 
can take pictures that will be satisfactory. Minor equipment 
is all that is necessary to make pictures of star trails, records 
of sunspots and the phases of an eclipse; but if an equatorial 
mounting is obtainable, comets, minor planets, star clusters, 
and glorious star fields fall within reach. Lunar landscapes do 
not require much equipment, but considerable care and 
experimentation are necessary to get sharp, unmoved, and 
satisfactory images. 

The first experiment in the new field for the amateur should 
be photographing the stars with a stationary camera. This will 
result in what are known as star trails (made because of the 
earth's rotation). These are obtained by lengthening the 
usual time of exposure considerably. As the earth swings on 
its axis, it carries the camera with it, and the stars, which 

remain still, form lines of light on the plate. 

109 



no Handbook of the Heavens 

Very firmly propped, the camera may be left open for any 
length of time. Longer exposures, of course, result in longer 
star trails, but it is not advisable to leave the shutter open 
more than four hours. The most interesting phase of star- 
trail photography is making circumpolar trails trails of the 
Pole Star and its immediate neighbors. When examined, trail 
pictures of this region will show a series of small and large 
concentric arcs, different indeed from the arcs of great circles 
made by stars directly overhead or by those 90 from the 
pole. 

To take pictures of this type, center the camera on the 
pole star and focus with a magnifier. It may be somewhat 
difficult to line up a box camera on Polaris because the star 
does not show up well in the small finder used with these 
instruments. Fortunately, this may be done fairly accurately 
if the observer takes a little care. Carefully avoid having 
any extraneous light coming into the lens while the plate is 
exposed. On cool summer evenings dew may collect on the 
lens and it is necessary that it be wiped off at intervals. The 
extremely cautious use of a flashlight will help in this, especially 
since it will provide enough light so that the lens may be 
cleaned without accidentally moving the camera. During 
exposure, the shutter should be opened to its widest aperture 
so that it will record the faintest stars possible, although the 
widest aperture does not give as good definition of image as a 
somewhat smaller one does. 

The best exposure for obtaining good results on circumpolar 
trails is from two to three hours. If the shutter be left open 
longer than this, the trails overlap too much. Pictures of this 
nature should be taken with a fast plate or film and should 
be developed for contrast. If the film is sent to a professional 
finisher for development, it would be wise to include instruc- 
tions both to develop for contrast and to print the pictures, 
whether or not they seem to have "turned out." Otherwise 
the finisher may return the negatives without making prints. 

When these circumpolar pictures are examined, it becomes 
obvious that Polaris is not right at the north celestial pole, 



Amateur Astronomical Photography 1 1 1 




Girard Block, J. A. C. Robert Fleischer, J. A. C. 

ORION. Orion, king of the winter ON THE TRAIL OF THE SET- 

skies, as photographed by an amateur. TING SUN. The moon, with the planet 

Made with long exposure, and with the Venue close beside it, dips toward the 

" telescope and camera guided on the western horizon. Long exposure with 

stars. stationary camera. 

for it has made a small arc of its own on the plate. By using a 
lens of large actual diameter and giving the plate a maximum 
exposure of about three hours, it is possible for you to photo- 
graph certain of the faint stars which are nearer the pole than 
Polaris and which will appear as short concentric arcs within 
the trail of the pole star. 

Pictures of the seas, plains, craters, and mountain ranges 
of the moon may be made with only two pieces of equipment 
a telescope and a camera. But what patience and experience 
are needed! Most cameras of the folding or pocket type are 
equipped with a lens that can be removed and should be taken 
off. Rigidly and carefully, the camera should be attached to 
the eyepiece end of the telescope, with the eyepiece racked out 
somewhat beyond the normal point. 

A ground-glass attachment is a necessary part of the 
camera's equipment for this work since the moon must be 



112 Handbook of the Heavens 

focused accurately with a magnifier. Without such an attach- 
ment it is practically impossible to focus the image correctly, 
although trial-and-error attempts may be made by setting 
the focus at various points, making pictures and developing 
to find which is best. 

Both instruments must be mounted rigidly in this work, 
and the greatest difficulty with a small telescope will probably 
lie in still having it centered on the moon when the picture is 
taken. A sight along the barrel of the telescope or a smaller 
finder telescope will help here. The actual exposure of the 
plates should be about % second for the supersensitive 
panchromatic films or plates that are recommended. A longer 
exposure blurs the moon's image from the diurnal motion, 
and with a long-focus telescope objective even the shorter 
time will "move" the image. 

An alternative to the foregoing method is to use the object 
glass (large lens) of the telescope only, removing the eyepiece 
and focusing directly on the ground glass. This " primary" 
image formed by the objective will be much smaller but 
much more under control. In this case the telescope itself is 
being used as a camera. Finest grain plates and fine-grain 
developer are necessary to this method which is used success- 
fully with home-made reflectors. Still a third method is to use 
the telescope complete and the camera complete, rigidly 
mounted back of the ocular, with a space of an inch between 
ocular and camera lens. The image is large and therefore moves 
rapidly because of the earth's rotation, but this method has 
proved successful. 

Beautiful photographs of constellations, star fields, comets, 
asteroids, and other special objects can be made if one has an 
equatorial mounting (described on page 95). Such a mounting 
can be constructed by anyone who is handy with tools, or one 
may be occasionally "picked up" here or there for a small 
sum. In all probability this mounting will not be motor driven, 
and it will be necessary to operate it by hand. A little practice, 
however, will enable you to keep the telescope moving so as 
to counteract the movement of the earth. 



Amateur Astronomical Photography 




Ramiro Qufjada, A. A. A. 

MOON. Mountain ranges, craters, and so-called "seas" are revealed in this photograph of 
the moon, taken with a homemade telescope. 

The polar axis of the mount must, of course, be lined up 
accurately with the north celestial pole, and the camera 
should be fixed firmly to the rest of the instrument. If the 
mounting is already serving a telescope, the camera had best 
be placed on top of it and fixed so that its focus is parallel to 
the telescopic line of sight. 

Should there be no telescope on the mounting, a small 
one must be attached at the same angle at which the camera 
is tilted. Cross-hairs, placed within the focus of the telescope's 
eyepiece, will enable the astrophotographer to keep the star 
or object under observation constantly in the center of the 
plate. The telescope must be guided throughout the length of 
exposure and the star must be kept precisely at the cross- 



114 Handbook of the Heavens 

hairs every second of the time. High magnification in the 
telescope will result in more efficient guiding of the mount. 

Camera work with comets and asteroids as subjects has an 
additional obstacle to overcome in that these bodies move 
noticeably in comparatively short periods of time. Therefore, 
when working with comets, the observer must guide most 
carefully on the comet head and, when he has developed his 
plates, he will find that the stars themselves have trailed. If 
he had guided on the stars, the comet would have trailed, thus 
ruining any structural details the picture might have shown. 

This same procedure is used in photographing asteroids if a 
disk is required or if the asteroid is so faint that the advantage 
of exposure is needed. Otherwise the asteroid will trail and the 
stars will appear as points of light. Especially in the discovery 
and recording of asteroids this last method is used. 

The equipment used in taking pictures of the moon may 
also be, used to take pictures of sunspots. The only accessory 
needed is a neutral filter to cut out the overpowering glare of 
the sun itself (such filters can usually be obtained at stores 
dealing in photographic goods). The procedure for sunspot 
pictures is the same as that for the moon landscapes. 

With nothing more than an ordinary camera and a little 
judgment it is possible to take photographs of the brighter 
planets including Venus, Mars, Jupiter, and sometimes 
Mercury. 

The camera need only be pointed at the subject and given 
an exposure of a few seconds (three or four) on fast plate or 
film. If the period of exposure is too long, movement of the 
subject across the plate will result from the earth's^ diurnal 
motion; and if it is too short, faint objects will not show. Six 
seconds is about the maximum exposure for this type of work 
with a small camera. The picture taken, of course, will be very 
small and it will be necessary to make an enlargement to 
show satisfactory results of your experiments in elementary 
astrophotography. 



Observational Scrapbook 

AWAY up in the extreme northern region of the moon, flanking 
the north border of Sinus Iridum, is located a mountain- 
ringed plain that contains one of the prime mysteries of lunar 
observation. There, in the depths of Plato, lies what? 

For years, Prof. William H. Pickering has carefully 
observed that crater and has watched color changes taking 
place. These, he suggests, are caused by vegetation. And there 
is no proof that they are not, for at the bottom of Plato there 
may be some remnant of oxygen or water to support plant life. 

Whatever their cause, the changes continue to occur. 
They appear as spots and streaks on the crater floor which 
vary in visibility independently of the sun's altitude and are 
prominent enough so that they may be seen with the aid of a 
6- to 12-inch telescope. The first step is to locate Plato on 
the moon with the aid of the maps (see page 58). The crater 
is prominent because of its unusual coloring and will be easy 
to find. 

There are a few elementary but important things to take 
into consideration in observing the changing conditions in the 
crater's depths. All observations must be made when the moon 
is in exactly the same phase, the moon should always be the 
same distance above the horizon, and the same magnification 
should be used each time. All these conditions must be equal- 
ized, and even then there is a chance of error due to atmos- 
pheric irregularities, so that numerous observations should 
be made before any changes noted can definitely be said to 
be taking place at the bottom of Plato. 

***** 

Travel has an interesting effect on the positions of heavenly 
bodies. In Florida the moon is often seen north of the zenith, 
its beams shining on the landscape from almost overhead. 
This naturally is because the moon must follow the zodiac, 



1 1 6 Handbook of the Heavens 

never straying from its border. The zodiac runs nearly over- 
head in Florida, but for New York the nearest it comes to the 
zenith is about 7?^. 

As we travel south, some stars climb up before us while 
others drop to our rear. In Florida the Dipper sets, as do others 
of our circumpolar constellations, but their loss is more than 
made up for by many new groups we see. The Southern Cross 
rises above the horizon for a short time, and Canopus is also 
visible, shining steadily in the clear air of the peninsula. 

At any point situated along the equator, Orion is directly 
overhead, but much below the equator he stands on his head 
because the ancients who figured the group lived in the 

northern hemisphere. 

***** 

It pays to keep your eyes open in everyday life, and also 
in astronomy. Know the stars, be familiar with each constella- 
tion, at* least to the extent of knowing all the prominent stars. 
And keep watch on them; glance up at the sky on clear even- 
ings and note the new constellations that are rising and those 
that are setting. Amateurs who have formed this habit are 
sometimes the ones who first discover the rare variety of 
stars called novae that spring from obscurity to many times 
their former brilliance, becoming prominent overnight. 

Shining brilliantly among the familiar stars, these novae 
(new stars) are conspicuous and are noticed immediately by 
one who is acquainted with the constellations. And they have 
been first discovered, on several occasions, by an amateur who 
was armed with no more than a thorough knowledge of the 

star groups. 

***** 

Millions of meteors daily meet extinction in their mad 
flight through the atmosphere, but despite this fact hundreds 
of them must actually reach the ground. The number which 
might be found lying about on any given unit of the earth's 
surface, however, is small because the earth itself is so vast. 
Frequently amateurs find rocks which, after a casual examina- 
tion, they take to be meteorites and which usually are merely 



Observational Scrapbook 117 




American Museum Photograph. 

AUNIGHITO. This meteorite, the Ahnighito iron of 37^ tons, is the largest in any 
museum today. It rests in the American Museum of Natural History, New York. Dark and 
cold now, its surface was once heated to incandescence by friction generated in a rapid 
flight through the atmosphere. 

pieces of basalt or some black rock. Persons familiar with 
rocks may be more certain of a suspected meteorite, for by 
elimination, if it is not a known rock, it may be a meteorite. 

The tentative identification may be checked by considering 
these points: the outer coating of meteorites often will be 
fairly smooth as a result of the oxidation caused by friction 
as they pass through the air; they may be any size, from a 
pebble to a rock weighing tons; and they may be heavier 
than other stones when picked up because many contain a 
large percentage of iron. The final analysis, which must be 
made in the laboratory for absolute certainty, will tell the true 
story, leaving no room for doubt. 

***** 

An amateur astronomer, attempting to find his way in the 
sky with nothing more than his sense of direction to guide him, 
would become hopelessly lost in a sea of stars even as an 
amateur navigator, with no knowledge of latitude and longi- 
tude, would become lost in the limitless wastes of an ocean. 

Early astronomers, realizing this, set about the task of 
providing themselves with a set of coordinates with which 
they could locate a star. To do this, they evolved a system of 
reference based on altitude and azimuth. 



Handbook of the Heavens 




O = observer 
Z = zenith 
Altitude and azimuth 
AX = altitude, 38 
SA azimuth, 90 -f- 
ZXAZ' = vertical circle 



CELESTIAL COORDINATES 

cp = vernal equinox P north celestial pole 

X = star NPZS = meridian 

Right ascension and declination 
BX declination, 40 
^ B = right ascension, 3)1 
PXP' = hour circle 
SZPXB = hour angle 



The altitude, or elevation of a star above the horizon as 
measured in degrees of arc, gave the height of a star above the 
horizon, let us say, 38. This one direction would be of little 
help, however, for this star might be located anywhere along 
a circle running around the sky parallel to the horizon and at an 
altitude of 38. The astronomer needed another coordinate. 

So he took the distance, measured in degrees westward 
around the horizon, from the due south point to the point 
directly beneath the star in question and called it azimuth. 
Now the star had an altitude of 38 and an azimuth, let us 
say, of 90+ to establish its position in relation to the observer. 

It is obvious, of course, that such a system is based upon 
the observer and that he is the primary point of reference. He 
sets up a framework through which he views the stars. But the 
stars' positions change their relation to this framework 
with every moment of time because of the earth's rotation. 
The background of stars seems to move in relation to the 
point of reference, therefore, and in the course of an hour a 
dozen stars might occupy the position of 38 altitude and 90+ 



Observational Scrapbook 119 

azimuth. Because of this, the altitude and azimuth system is 
used today for certain limited purposes, as for navigation. 

Most generally, astronomers employ that set of constants 
known as right ascension and declination. 

Since there are in the sky both a north and south celestial 
pole where the axis of the earth, projected, intersects the 
celestial sphere, one may rightly institute a celestial equator, 
situated midway between the poles, and everywhere at a 
distance of 90 from them. 

From this sky equator is measured declination the 
distance in degrees north or south of the equator, positive (+) 
if north, and negative ( ) if south. It corresponds to latitude 
as measured on the earth's surface, and it provides the 
astronomer once again with one of the two coordinates neces- 
sary to find the position of an object on the celestial sphere. 

The ecliptic, a great circle on the celestial sphere, is formed 
by the intersection of the plane of the earth's orbit on the 
celestial sphere. It intersects the celestial equator at two 
points, the vernal and autumnal equinoxes. 

Through the vernal equinox, which lies in the southern 
part of the constellation of Pisces, astronomers have drawn 
an imaginary line, a great circle running from pole to pole 
around the sky for 360, and they have called it the equinoctial 
colure. This line, as are all others bisecting the celestial sphere 
at the poles, is known as an hour circle. And every star has 
its own hour circle, running through it and through the 
celestial poles. Right ascension, the second of the two coordi- 
nates, is measured in degrees eastward on the celestial equator 
from the vernal equinox to the point where the star's hour 
circle cuts the equator. 

Under this system when an astronomer wishes to locate a 
particular object on the celestial sphere, he may use right 
ascension and declination in a manner similar to that in which 
latitude and longitude are used by mariners. All standard 
atlases are based on this system, and it is also employed in the 
operation of an equatorial telescope. With right ascension and 
declination tables given, it is possible to locate any celestial 
object at any time. 



(glossary 



Aberration, chromatic: 
Aberration, spherical: 

Aphelion: 
Apochromat: 

Asteroids: 

Binary, spectroscopic: 

Celestial sphere: 
Configuration: 

Coordinate: 
Declination: 

Degree : 

Earthshine: 
Eclipse, lunar: 
Eclipse, solar: 
Ecliptic: 

Elongation, greatest: 
Ephemeris: 

Equator, celestial: 



The condition of a telescope lens in which all the colors of 
the image are not brought to one focus. 
The condition of a telescope lens in which the marginal 
and central rays of the image do not come to a focus at the 
same point. 

Point in the orbit of an object farthest distant from the 
sun. 

A lens of the highest possible correction where the differ- 
ent color components of white light all come to a focus in 
one plane. 

The minor planets or planetoids whose orbits lie between 
the orbits of the planets Mars and Jupiter. 
A system of two stars revolving about each other in which 
the separate stars cannot be seen with a telescope although 
they can be detected with the spectroscope. 
The infinitely remote imaginary globe suspended around 
the earth, on which the celestial objects are projected. 
The grouping of stars and planets in recognizable pattern 
for identifying. This term is usually used to identify the 
planet's position. 

One of two points of reference on the celestial sphere used 
to determine the position of an object. 
The celestial coordinate measured north or south of the 
celestial equator; a star's distance north or south of 
celestial equator. 

A unit of measurement on the celestial sphere () (any 
circle is 360 degrees) further divided into minutes (') 
each of which contains 60 seconds (") 
A slight illumination of the dark portion of the moon by 
light reflected from the earth. 

A cutting off of the sunlight received by the moon when 
it passes into the earth's shadow. 

A cutting off of the sun's light by the passage of the moon 
across the sun's disk. 

A great circle made by the intersection of the plane of the 
earth's orbit with the celestial sphere. The apparent 
path of the sun through the sky lies along this circle. 
The points in the apparent paths of Mercury and Venus 
where they are at their greatest distance east or west from 
the sun as seen from the earth. 

Tables of the prediction of the exact location of an object 
at stated times; The American Ephemeris is published by 
the United States Naval Observatory and contains this 
for the sun, moon, planets, etc. 

The earth's equator projected to the celestial sphere. It is 
121 



122 



Handbook of the Heavens 



Equatorial mounting: 
Equinox, vernal and autumnal 

Equinoxes, precession: 

Equinox of a chart: 

Eyepiece: 

Eyepiece, Huygenian: 

Faculae: 

G. C.T.: 

Guiding: 
Hour circle: 
Interpolation: 

Magnitude: 
Maria: 

Meteor: 



Meteorite: 
Meteor shower: 
Messier* s Catalogue: 



Nebula, dark: 

Nebula, planetary: 
Nebulae, spiral: 

Nova: 



a great circle on the celestial sphere, everywhere 90 from 
the celestial poles. 

Type of telescope mounting consisting of a polar axis set 
parallel to the earth's axis and of a declination axis at 
right angles to the polar axis. Graduated circles relating 
to right ascension and declination are attached to the axes. 
Imaginary points in the sky where the celestial equator 
and the ecliptic cross. The sun reaches these points on 
March 21 (vernal equinox) and September 23 (autumnal 
equinox). 

The slight westward movement of the equinoxes, or the 
slow conical movement of the earth's axis around a line 
connecting the poles of the ecliptic. 

The exact position of the coordinates of the chart with 
respect to the background of stars. 

The short-focus lens or combination of lenses which is 
nearest the eye in a telescope. 

A type of eyepiece invented by the noted astronomer 
Huygens, sometimes called the "negative eyepiece." 
The regions surrounding sunspots which are much hotter 
than the average solar surface and therefore are seen as 
white spots in contrast to the sun's yellow-white surface. 
Greenwich Civil Time means solar time of the prime merid- 
ian at Greenwich, zero hour in all astronomical computa- 
tions. o h G. C. T. = 7 P.M. Eastern Standard Time. 
The moving of a telescope or of the photographic plate to 
keep an object exactly in the same place on the plate. 
A great circle which passes through a celestial object and 
through the celestial poles. 

The process of deriving from a series of given values, other 
intermediate values in conformity with the given values. 
The brightness of a star or other celestial object. 
The large, darker areas of the moon; the so-called "seas," 
now known to be arid plains. 

To the observer a brilliant flash of light in the sky, some- 
times called a "shooting star"; actually a bit of solid 
matter passing through the earth's atmosphere from 
outer space. 

A meteor that has reached the earth's surface. 
A swarm of meteors which returns periodically. s 
A very famous catalogue of the most splendid star clusters 
and nebulae found in the heavens, compiled by Messier. 
The objects are designated by the initial M and a number 
(example, M 31 great Andromeda Nebula). 
Patches of cosmic dust which shut off the light of stars in 
the background and which do not reflect light. 
Disklike masses of nebulosity surrounding a central star. 
(Island universes). Great aggregations of stars, star clus- 
ters, lesser nebulae, etc., which have a physical connection. 
A new star seen where none or only* a dim star was seen 
before. 



Glossary 



123 



Objective, achromatic: 



Objective: 

Ocular: 
Occultation: 

Opposition: 

Perihelion: 
Prominence: 

Revolution: 
Right ascension: 



Rotation: 
Solstice, summer: 

Solstice, winter: 
Spectroscope: 

Star: 
Sun: 
Sunspots: 

Telescope, reflecting: 
Telescope, refracting: 
Terminator: 
Transit: 

Variable, cepheid: 
Variable, eclipsing: 

Variable star: 

Zenith: 

Zodiac: 



The type of objective usually composed of two lenses, a 
double-convex lens of crown glass and a plano-concave lens 
of flint glass, used to correct chromatic and spherical 
aberration. An ordinary "good" lens. 
The large lens of the telescope, which is used to form the 
primary image of the object observed. 
The eyepiece of a telescope. 

The hiding of one celestial object by another larger celes- 
tial object (usually the moon). 

Position of a superior planet when sun, earth, and planet 
are in straight lines, and in this order. 
Point in the orbit of an object nearest the sun. 
A large, gaseous, incandescent offshoot of gas seen at the 
edge of the sun. 

The motion of one body about another. 
The celestial coordinate measured eastward from the 
vernal equinox along the celestial equator; a star's dis- 
tance from the vernal equinox measured along the celestial 
equator to the star's hour circle. 
The motion of any body on its own axis. 
The time when the sun reaches its highest north declina- 
tion point. Usually June 21. 

The time when the sun is at its greatest point of south 
declination. Usually December 22. 

An instrument used to determine the composition of the 
sun and stars by spectrum analysis. 
A great ball of burning gas. 
A star or great ball of burning gas. 

Dark areas in the sun's surface, believed to be magnetic 
storms. 

A type of telescope employing a concave mirror as the 
main optical part. 

A type of telescope employing a compound-convex lens as 
the main optical part. 

The boundary between the light and the dark side of a 
body. 

The crossing of a celestial object in front of the disk of an 
apparently larger body; or the passing of a celestial body 
across the field of view of a telescope. 
A type of variable star named after the first star of its kind 
ever discovered, Delta Cephei. 

A binary star, made variable by the eclipsing of one com- 
ponent by the other. 
A star that changes its brightness. 
The point exactly overhead. 

A band of twelve constellations, 8 either side of the 
ecliptic; the zone in which the sun, moon, and planets 
seem to move. 



124 



Handbook of the Heavens 



The Greek Alphabet 



a Alpha 


t\ Eta 


? Nu 


/SBeta 


Theta 


Xi 


7 Gamma 


t Iota 


o Omicron 


5 Delta 


K Kappa 


TT Pi 


6 Epsilon 


X Lambda 


p Rho 


fZeta 


M Mu 


<r Sigma 



r Tau 
v Upsilon 
4>Phi 
xChi 
^ Psi 
w Omega 



INDEX 



Aberration, chromatic, 98, 121 

Achernar, 17, 34 

Ahnighito meteorite, 117 

Albireo, 12, 13, 25, 69, 71, 73 

Alcor, 6, 24, 69, 70 

Aldebaran, 14, 15, 37, 55, 85 

Algol, 8, 89, 91 

Alphard, 24, 25 

Alps, lunar, 54 

Altair, 12, 13, 25 

Altazimuth telescope mounting, 95, 

9 6 

Altitude, 117-119 
American Association of Variable 

Star Observers, 91, 93 
American Meteor Society, 63 
Andromeda, 13, 28 

Gamma, 73 

great nebula in, 13, 80-83 
Antares, 26, 27 
"Apochromat" lens, 98, 121 
Appenines, lunar, 54 
Apus, 33, 35 
Aquarius, 27, 82 
Aquila, 12, 13, 25 
Ara, 33, 34 
Arcturus, 23-25 
Argo Navis, 17 
Aries, 13, 28 
Aristarchus, 54 
Aristillus, 53 
Aristoteles, 53 
Asteroids, 41, 42, 98, 101-109, II2 ~ 

114, 122 

description of, 101 



Asteroids, discovery of, 101 
observation of, 41, 102-106 

Astronomisches Rechen-Institut, 
102 

Auriga, 17, 22, 91 
clusters in, 86 

Autumnal equinox (see Equinoxes) 

Averted vision, 99 

Azimuth, 117-119 

B 

Baily's Beads, 77 

Bear, Greater and Lesser (see Ursa 

Major; Ursa Minor) 
Bee-Hive cluster (see Praesepe) 
Bellatrix, 15 
Betelgeuse, 15 

Binary stars, 69-71, 89, 97, 99 
eclipsing, 72 

(See also Double stars; Kriiger 

60) 

Bootes, 23, 24, 73 
Epsilon, 73 



Camelopardalis, 8 
Campbell, Leon, 93 
Cancer, 16, 17 

clusters in, 86 
Canes Venatici, 23, 24 
Canis Major, 15, 16, 22 

(See also Sirius) 
Canis Minor, 15, 16, 22 
Canopus, 29, 32, 33, 116 
Capella, 17, 63 
Capricornus, 27, 69 

Alpha, 69 



125 



126 



Handbook of the Heavens 



Carina, 32, 33 

Eta, 33 

Carpathians, lunar, 54 
Cassini division, 43 
Cassiopeia, 7, 22, 26, 91 

Eta, 70 
Castor, 1 6, 73 
Celestial equator, 119, 121 
Celestial sphere, 118, 119, 121 

(S^ also Coordinates, astro- 
nomical) 
Centaurus, 32, 33 

Alpha, 32 

Omega, 32 
Cepheus, 8, 26, 88, 91 

Delta, 8, 26, 91 

Mu, 26 
Ceres, 13, 101 
Cetus, 13-15, 34, 35 

Omicfon (see Mira) 
Chamaleon, 35 
Chi-h Persei, 8, 84, 86 
Circinus, 32, 33 
Circumpolar stars, 5, 8, 17, no 

explanation of, 8 
Clavius, 53 
Clusters, 8, 12, 26, 29, 32, 34, 35, 

71, 80, 84-87, 99 
Columba, 15, 16 
Coma Berenices, 23, 24 
Comets, 61, 65-68, 105, 109, 112- 

114 

composition of, 65 

designation of, 66, 67 

discovery of, 66 

disintegration of, 61, 67 

Donati's, 66 

Encke's, 68 

Halley's, 67 

observation of, 66, 98 

orbits of, 67 

structural detail and size of, 65 



Coordinates, astronomical, 104, 

II7-II9, 121 

Copernicus, 53 

Cor Caroli, 23, 24 

Cor Hydrae (see Alphard) 

Corona, 23-26 

solar, 77-79 
Corvus, 24, 25 
Crater, 24, 25 
Crepe ring, 43 
Crisium, Mare, 51, 52 
Crux, 29, 32-34 

Kappa, 29 
Cygnus, 12, 13, 25, 26, 69, 71, 82 

Beta, 69 



D 



Declination, 96, 104, 119, 121 

Deimos, 40 

Delphinus, 12, 13, 63 

Deneb, 12, 13, 23, 25 

Denebola, 23 

Diamond of Virgo, 23 

"Diamond Ring," 77-79 

Dione, 44 

Dipper (see Ursa Major) 

Dorado, 32, 34 

Double stars, 6, 7, 22, 23, 69-73, 89, 

97, 99 

classification of, 69, 71 

discovery of, 70 

list of, 72 

observation of, 73 
Draco, 6, 7 

Alpha, 7 
Dumbell Nebula, 82, 83 



Earth, 7, 14, 37, 39, 96, 118 
Earthshine, 52, 121 



Index 



127 



Eclipses, 55-57, 76-79, 109 
lunar, 56, 57, 121 

solar, 57,76-79, 121 
Ecliptic, 14, 118, 119, 121 

(See also Zodiac) 
Elongation, 37, 121 
Encke's Division, 43 
Ephemeris, 42, 97, 102, 103, 121 
Equator, celestial, 14, 91, 118, 121 



H 



Hadley, Mt., 53 

Harvard Observatory, 66, 93 

Hercules, 6, 15, 24, 26, 35, 84 

globular cluster in, 26, 35, 84 
Herschel, Sir John, 34 
Herschel, Sir William, 16, 44, 70, 
81,87 



Equatorial telescope, mounting, Herschel solar prism, 54, 75 



95-97, 112, 119 
Equinoctial colure, 119 



Horologium, 35 
Horsehead Nebula, 82 



Equinoxes, 13, 14, 22, 27, 104, 119, Horseshoe Nebula (Mi7), 82 



122 

autumnal, 122 

precession of, 22, 27, 104, 122 

vernal, 13, 14, 119, 122 
Eridanus, 14, 15, 17, 34 

Gamma, 34 

Omicron, 34 
Eros, 102 
Evening star, 37, 38, 46 



Hour angle, 96 
Hour circle, 96, 119, 122 
Humorum, Mare, 52 
Huygens, Mt., 54 
Hyades, 14, 85, 86 
Hydra, 24, 25 
Hydrus, 32, 34 



Faculae, 74, 75, 122 
False Cross, 33 
Fireballs, 60 
Foecunditatis, Mare, 51 
Fomalhaut, 14, 15, 27 
Fornax, 34, 35 
47 Toucanae, 35 
Frigoris, Mare, 52 



Gemini, 16, 22, 85, 87 
clusters in, 87 
Delta, 16, 45, 87 
Eta, 16, 87 

Grimaldi, 53 

Grus, 35 



lapetus, 44 

Imbrium, Mare, 52, 54, 58 

Indus, 33, 35 

Insolation, 76 

Iridum, Sinus, 52, 115 



j 



Juno, 101, 106, 108 

chart of, 108 
Jupiter, 41, 42, 44, 46, 50, 62, 68 

chart of, 50 

gravitational attraction of, 62, 68 

moons of, 41, 42 

red spot of, 41 



K 



Kriiger 60, 70, 73 



128 



Handbook of the Heavens 



Lacerta, 8 
Leibnitz range, 54 
Lenses, 94, 95 

(See also Telescopes) 
Leo, 22, 23, 81, 87 

clusters in, 87 

Gamma, 22 

nebulae in, 81 
Leo Minor, 23 

Leonid meteor shower, 22, 61 
Lepus, 15, 35 
Libra, 23, 27 

Lowell Observatory, 16, 45 
Lynx, 8 
Lyra, 12, 13, 25, 26, 80 

Epsilon, 25, 69 

ring nebula in, 13, 80, 81 

M 

Magellanic clouds, 29, 32, 33-35 

black, 29 

greater, 33 

lesser, 34, 35 
Maginus, 53 

Magnitude, explanation of, 7, 122 
Maria, of moon, 51, 52, 122 
Mars, 39-41, 46, 49, 101 

canals of, 39, 41 

chart of, 49 

moons of, 40 

polar caps of, 40 
Medii, Sinus, 52 
Mensa, 34, 35 
Mercury, 37-39, 45-47, 101 

chart of, 47 

phases of, 38 
Meteor showers, 7, 61-64, 67, 122 

chart for recording, 64 

list of, 64 
Meteorites, 116, 117, 122 



Meteors, 60-64, IJ 6, 117, 122 

composition and size of, 60, 61 

observation of, 60, 62, 63 

origin of, 61, 67 

Milky Way, 8, 17, 25-27, 29, 83, 85 
Milky Way Galactic System, 81, 

83-85 

Mira, 13, 14, 89 
Mizar, 6, 24, 69, 70 
Monoceros, 15, 16, 86, 87 

clusters in, 87 

Moon, 3, 4, 14, 1 6, 51-59, 76, 109, 
111-113, I J 5> II6 

bays of, 52 

craters of, 53 

eclipses of, 55, 56 

map of, 59 

marshes of, 52 

mountain ranges of, 54 

mountain walled plains, 53 

occultations, 55, 56 

Oceanus Procellarum, 52 

phases of, 51, 52 

promontories of, 52 

ray systems of, 53, 54 

seas of, 51, 52 

Straight Range, 55 

Straight Wall, 54 

surface of, 51 
Morning star, 37, 38, 46 
Multiple stars, 71 
Musca, 35 



N 



"Nautical Almanac," 97 
Nebulae, 23, 33, 34, 80-83, 85, 99, 

122 

Andromeda, great, 80, 81 
classification of, 80, 81 
coal sack, 26, 29 
dark, 82, 83 
diffuse, 81 



Index 



129 



Nebulae, Orion, great, 80, 81 

planetary, 34, 80, 81 

spiral, 13, 80-82 
Nebularum, Palus, 52 
Nectaris, Mare, 51 
Neptune, 22, 45-46, 50, 98 

chart of, 50 

moons of, 45 
Norma, 33, 34 
North Star (see Polaris) 
Northern Cross (see Cygnus) 
" Norton's Star Atlas," 100 
Nova Herculis, 89 
Novae, 89, 116, 122 
Nubium, Mare, 52, 55 

O 

Occultations, 14, 55, 56, 123 
Oceanus Procellarum, 52 
Octans, 35 

Sigma, 35 
Ophiuchus, 15, 26, 83 

dark nebulae in, 83 
Orion, 15, 16,22, 29,34,35,63,71, 
80, 81, 83, in, 116 

dark nebulae in, 83 

great nebulae in, 15, 71, 80, 81 



Pallas, 101 
Pavo, 33, 35 
Pegasus, 12, 13, 28 
Perseid meteors, 7, 62 
Perseus, 7, 22, 84, 86, 89, 91 

Beta, 89 

Chi-h, 8, 84, 86 

clusters in, 86 
Phases, 38, 39, 51-53 

of Mercury, 38 

of Moon, 51-53 

of Venus, 38, 39 



Phobos, 40 

Phoenix, 34, 35 

Photography, astronomical, 66, 82, 
102, 109-114 

of asteroids, 109, 112-114 
of comets, 109, 112-114 
of eclipses, 109 
of moon, 109, 111-113 
of planets, 114 
of star fields, 109, 112, 113 
of star trails, 109, no 
of sunspots, 109, 114 

Pickering, Prof. William H., 54, 115 

Pisces, 13, 14, 119 

Piscis Austrinus, 14, 27 

Plato, 54, n 5 

Pleiades, 13-15, 82, 85, 86 

Pluto, 1 6, 45 

Pointers, 63, 69 

Polaris, 6, 7, 63, no 

Poles, celestial, 5-8, no, 119 

Pollux, 16, 73 

"Popular Astronomy," 93 

Praesepe, 16, 17, 86 

Procyon, 15, 1 6 

Prominences, solar, 77, 79, 123 

Proxima Centauri, 32 

Ptolemaeus, 53, 54 

Puppis, 16 

Putredinus, Palus, 52, 54 

Pyxis, 1 6 

R 

R Coronae, 89 
R Leonis, 91, 92 
Radiant, meteor, 7, 61, 62 
Regulus, 22-24 
Retrograde motion, 42 

of planets, apparent, 40, 45 
Rhea, 44 
Rho Persei, 8, 90 
Rigel, 15, 34, 63 



130 



Handbook of the Heavens 



Right Ascension, 104, 119, 123 
Riphacn mountains, 54 



S Doradus, 32, 34 

Sagittarius, 26, 27, 37, 82, 85-87 

clusters in, 87 
Saturn, 3, 42, 46, 50 

chart of, 50 

moons of, 44 

rings of, 42, 43 
Schickard, 53 

"Schurig's Star Atlas," 100 
Scorpio, 26, 27, 33 
Scutum, 26 
Serenitatus, Mare, 51 
Serpens, 24, 26 
Sextans, 24, 25 
Shadow Bands, 78, 79 
Shapley, Harlow, 32 
"Shooting stars" (see Meteors) 
Sidereal clock, 97 
Sirius, 7, 12, 15, 16, 22, 25, 33, 37, 

38,41 

Solar system, 24, 25, 42, 61 
Somnii, Palus, 52 
Southern Cross (see Crux) 
Spectroscope, 71, 79, 123 
Spectroscopic double stars, 71 
Spectrum analysis, 71 
Spectrum, Flash, 79 
Spica, 23-25 

Star clusters (see Clusters) 
Star trails, 109, no 
Stars, changes with seasons, 14 
Straight Range, 55 
Straight Wall, 54 
"Stuker's Star Atlas," 100 
Sun, 3, 25, 32, 34, 37, 74~79, 9, 123 

eclipses of, 76-79 

observation of, 75 

rising and setting points, 76 



Sunspots, 74, 75, 77, 109, 114, 123 

description of, 74 

observation of, 75 
Syrtis Major, 40, 41 



Taurus, 13, 15, 16, 22, 35, 83, 85 

dark nebulae in, 83 
Telescopes, 7, 22, 70, 94-100, 103, 
112, 119, 123 

"finder" telescope attachment, 

99 

focal length, 94 
Lick 4O-inch refractor, 70 
magnification of, 94, 98, 99 
mounting of, 95~97, 112, 119 
types, 94, 112 
use of, 75, 96-100 

Telescopium, 34, 35 

Tethys, 44 

Theophilus, 53 

Theta Orionis, 15, 80 

Titan, 44 

Toucan, 34, 35 

Tranquilitatus, Mare, 51, 52 

Trapezium, 71 

Triangulum, 13, 28 

Triangulum Australe, 32, 35 

Trifid Nebula, 82, 87 

Triton, 45 

Tycho, 53 



U 



Uranus, 16, 44, 50, 87 

chart of, 50 

moon of, 44 
Ursa Major, 3, 5, 8, 23-25, 29, 63, 

69, 116 
Ursa Minor, 6 



Index 



V 



Vaporum, Mare, 52 
Variable stars, 8, 13, 26, 32- 
88-93, 123 

Cepheid type, 8, 88, 123 

classification of, 88, 89 

designation system of, 90, 91 

list of, 93 

observation of, 90-92 
Vega, 7, 12, 13, 25 
Vela, 32, 33 

Venus, 3, 38, 39, 41, 45, 46, 48, 
in 

chart of, 48 

phases of, 38, 39 



Vernal equinox (see Equinoxes) 
Vesta, 101, 105, 106, 107 

chart of, 107 
-34, Virgo, 23, 27 

nebulae in, 87 
Volans, 32 
Vulpecula, 82 



6 5> 



Zenith, 123 
Zenith prism, 97 

Zodiac, 3, 13, 1 6, 22, 37, 52, 115 
116, 123 

(S^ also Ecliptic) 
Zodiacal constellations, 3, 13, 16, 

17, 23, 27, 37, 45